CavMag

AUGUST 2014 Issue 12 News from the Cavendish Laboratory

Inside

The Top Quark and Going Beyond the Standard Model 3 Phase Transiting to a New Quantum Universe 4 Tony Hewish at 90 5 Nano-spintronics 6 Physics and Industry: Past, Present and Future 8 Richard Hills FRS 9 Rutherford Schools Physics Project - An update 10 Maxwell, the Ether and the Michelson- Morley Experiment 12 Upcoming changes to the Physics curriculum 14 Keeping the show on the road 15 How you can contribute 15 News 16

Cavendish awarded Athena Swan Gold Award

e are delighted that the Head of Department Andy Parker wrote: higher education across all four nations Cavendish Laboratory of the UK, and in colleges in Scotland. has been granted Athena “Our Equality and Diversity team, led ECU works closely with colleges and SWAN Gold Award status by Val Gibson and David Peet, have universities to seek to ensure that staff inW the 2014 Equality Challenge Unit’s been engaged in a long-term effort to and students are not unfairly excluded, Athena SWAN Scheme. To set this ensure that the Department provides a marginalised or disadvantaged because success in context, 125 UK departments welcoming and supportive environment of age, disability, gender identity, marital and universities applied for an Athena for our female staff and to remove or civil partnership status, pregnancy or SWAN award in this round, and 89 barriers to their progression. It is very maternity status, race, religion or belief, were successful in attaining Gold, clear that these measures have benefited sex, sexual orientation, or through any Silver or Bronze status. Only three all of our staff. I am proud that our combination of these characteristics or Gold awards were announced in the efforts have been recognised by the other unfair treatment.” April 2014 list, one of which went to Athena Swan panel.” the Cavendish Laboratory. We are the Val and David have spearheaded the first Department in the University to attain this status and the first Physics The objectives of the Equality Challenge Unit Cavendish’s efforts to implement these ECU Department in the UK with a gold (ECU) are described on their web-site. It works policies since the scheme started almost ten years ago. It is worth highlighting the many award. “…to further and support equality changes which have been made to bring the and diversity for staff and students in culture in the Laboratory into concordance

phy.cam.ac.uk Continued overleaf... Continued from overleaf

with the high expectations of the scheme. In the Cavendish’s submission, our application highlighted our main successes over the last 5 years as follows:

• a 64% increase in the number of women academic staff (3.2 FTE women appointed to Lecturer/Reader compared to 4 men); • all female academics, eligible for promotion, have been promoted at least once; • positive impact from the re‐design of our undergraduate Physics course and an action plan to address the performance of women undergraduates at the end of their first year; • a requirement that all staff undergo Equality and Diversity (E&D) training; • a significant expansion in career advice activities for research staff; • a review of the Staff Review and Development scheme, resulting in an increased coverage from 40% to 80% of the target cohort; • the formation of a very active Research Staff Committee (meeting termly) and associated events (monthly postdoc teas and targeted workshops); • a Workload Model for academic and senior research staff, in its second year of operation; • formation of the Cavendish Social Committee and associated events (meeting termly, with 2 or 3 events held each year); and • influential engagement with Athena SWAN and other gender equality activities at both the University and national levels.

Our full submission can be found at: www.phy.cam.ac.uk/Women-in-Physics/ WiPFiles/athena-swan-gold-application

University of Cambridge Vice-Chancellor Top and left: Practical physics classes. Professor Sir Leszek Borysiewicz described Bottom right: Aziza Suleymanzade (AMOP) and Anna-Lena Redman (BSS) having completed their workshop training course. the Department of Physics as a “beacon” within Cambridge:

“The Department was the first to gain an Athene Donald said: staff members are involved. These are Athena SWAN Award in the University wonderful achievements and an inspiration in 2010 and leads the way for other “I am delighted that the Department of for young women thinking about careers in University departments who now hold, Physics has been awarded Cambridge’s the physical sciences. Whilst we can relish or are working towards, Athena SWAN first Athena Gold. As the University’s the moment of success, we are well aware Awards. The University is extremely Gender Equality Champion, as well that the award is for three-years and we committed to progressing gender as a member of the department, it is need to continue all our efforts to maintain equality and we are beginning to see excellent to see this recognition of all the and enhance our present status so that it the impact of the significant resources hard work and far-sighted action being can be renewed in three years’ time. This and initiatives dedicated to improving carried out by Physics. I hope this will act is indeed as it should be and we can only the numbers of women across all career as a stimulus and inspiration for other applaud the continued efforts of everyone in stages. The Department of Physics departments in the University.” the Laboratory in contributing to our Gold has played and will continue to have a status. key role in supporting and promoting The February 2014 edition of CavMag women in STEMM (science, technology, (number 11) highlighted some of the Malcolm Longair engineering, maths and medicine).” many areas of physics in which women

2 CavMag AUGUST 2014 The Top Quark and Going Beyond the Standard Model

We are delighted to to continue his work on the top quark, (STFC). Thanks to additional financial welcome Alexander at that time among the least-known of support from the STFC, as well as from Mitov who joined elementary particles. It was at CERN that Cambridge’s Newton Trust, he has been the Laboratory Alex’s innovative projects came to fruition able to increase significantly the footprint of in 2013 as a and he, together with his long-time close Theoretical Particle Physics in the Cavendish University Lecturer collaborator Michael Czakon, published one Laboratory with the establishment of in Theoretical High of the most anticipated works in collider the new Centre for Precision Studies in Energy Physics. physics (Fig. 1). His groundbreaking papers Particle Physics. The Centre’s mission is Here he reflects on top-quark physics have the distinction of the development of a new generation upon his career to several ‘first-ever’ attached to them. of precision phenomenological particle date and his future physics applications and, ultimately, their programme. Going beyond these purely theoretical incorporation in the most important breakthroughs, Alex’s scientific results have analyses of data expected from the LHC and Born in the land of the mythical and empowered experimental collaborations future high-energy colliders. enigmatic Thracians, Alexander (Alex) Mitov at the LHC by offering new, qualitatively received his Master's degree in Physics different tools. By now his work has been In addition, he has just been offered a from Bulgaria’s oldest national university, utilised by these collaborations in their prestigious Senior Research Fellowship at named after St. Clement of Ohrid - a IX-th extensive searches for physics beyond the Durham University that will give him the century Bulgarian scholar, prolific writer and Standard Model and in their attempts to opportunity to spend a few weeks at the translator, often linked with the invention clarify with ever-increasing precision the UK’s premier particle physics Institute (IPPP) and popularization of the Cyrillic alphabet. ultimate validity of the fundamental laws of in Durham. physics, as embodied in the Standard Model Upon graduating from Sofia University, of the Elementary Particles. Alex was offered one of only two national scholarship awards that supported young Alex’s work has been generously supported Bulgarian researchers in the field of by a number of research agencies. At Mathematical Physics. A couple of years present, he is supported by an Ernest later he received a research fellowship from Rutherford Fellowship from the UK the University of Rochester in Rochester, NY, Science and Technology Facilities Council which offered him the opportunity to pursue research directly related to elementary particle colliders, such as the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland.

He obtained his MA and PhD degrees in four years, working with three different groups on independent research topics. Upon graduation, he accepted the offer of Kirill Melnikov, a prominent young scientist, to join his team as a post-doctoral research fellow at the University of Hawaii. It was in this tropical paradise that Alex became acquainted with the spirit of Aloha, the beauty of the endless Pacific and the thrill of surfing. He also managed to write several papers that led to the subsequent derivation of one of last decade’s strongest constraints on the possible existence of Physics beyond the Standard Model, which has so far proved so elusive. To date, this work has been cited close to 700 times.

Subsequently, Alex received a Humboldt Fellowship and the Inaugural LHC Theory Initiative Fellowship from the USA, both of Fig. 1. Measured and predicted top-antitop production cross sections in proton-proton and which presented him with the opportunity proton-antiproton collisions from Tevatron to LHC energies. The theoretical curves were to pursue independent research and join generated using the predictions by Czakon, Fiedler and Mitov (see M. Czakon, P. Fiedler and forces with some of the leading research A. Mitov, 2013. The total top quark pair production cross-section at hadron colliders through O(a 4). Physical Review Letters, 110, 252004 and the Particle Data Group Review 2013.) centres in Germany and in the USA. He was S then offered a 3-year fellowship at CERN

AUGUST 2014 CavMag 3 Phase Transiting to a New Quantum Universe

Fig. 1. The strontium titanate perovskite lattice. Titanium ions (red) and oxygen ions (gold) form electrical dipoles which line up in a ferroelectric state.

Recent insights and the discovery of a may line up resulting in ordered electric applications in optics and electronic devices. new class of quantum transition open fields permeating the crystal. By using When cooled below 50 K the crystals begin the way for a whole new subfield pressure, chemical, or isotopic substitution, vibrating with highly anharmonic quantum of materials physics and quantum ferroelectrics can be tuned into the quantum fluctuations which drastically change the technologies. critical regime where dipole fluctuations measured physical properties (Fig. 4). exist in an effective four-dimensional space Crucially the thermodynamic properties A recent article in Nature Physics [1] reports and arise due to criticality of the quantised depend upon the time dependent properties results on the quantum properties of polar lattice vibrations. This physics is very of the fluctuations, which is not the case ferroelectric crystals. In this project, led by different to that found in other quantum near a classical critical point. Stephen Rowley (top) and Siddharth Saxena critical systems which focus on electronic (middle) with Gilbert Lonzarich (bottom) or spin degrees of freedom. Intriguingly Going beyond ferroelectric insulators, of the Quantum Matter Group in the the fluctuation spectrum found in quantum electron charge carriers may be introduced, Cavendish, a new type of quantum phase critical ferroelectrics is the same as that in for example, by voltage gating or transition is explored in these seemingly elementary particle physics – propagating chemical substitution. The first of the

‘inert’ materials. modes in three spatial dimensions plus one oxide superconductors - doped SrTiO3, time dimension. discovered in the 1960s - is of this kind. Quantum phase transitions are subtly Superconductivity appears to arise in different from the familiar classical phase The article in Nature Physics highlights the intriguing anti-adiabatic limit which transitions, an example of which would the amazing transformation of the crystal poses a major challenge to theory. The be the freezing of water or the melting properties as a ferroelectric approaches its understanding of superconductivity in of ice as the temperature is changed. In quantum critical point. It describes how a SrTiO3 and KTaO3 have remained particularly such a transition, matter transforms into theory was developed to understand the elusive. New measurements and theory a more or less ordered state depending phenomena successfully and quantitatively led by the Cambridge team have shown on whether its temperature is decreased in a number of materials without adjustable how the novel polar optical phonons or increased. If, however, the temperature parameters (Fig. 3). The theory included the existing close to the ferroelectric quantum was hypothetically fixed at absolute zero effects of coupled fluctuating polarisation critical point can mediate this type of and another parameter, such as pressure, and quantum strain fields which explained superconductivity. This involves a gap was applied to bring about a transition, this the observation of small peaks in the function that oscillates in time to avoid would occur without any change in entropy, measured dielectric susceptibility below a repulsive parts of the time dependent that is, it would be an ‘order-to-order’ temperature of 4 K. electron-electron interaction potential. Such transition. In the neighbourhood of such knowledge is already guiding the search a zero entropy phase transition one often The most striking effects were observed in for new types of superconductor and other finds the emergence of superconductivity or the mineral strontium titanate (SrTiO3) using correlated states of quantum matter. other forms of novel quantum order. custom-built high-precision measurement apparatus developed in the Laboratory. Further unravelling the quantum nature

Ferroelectrics are materials comprising SrTiO3 crystals may be cut into beautiful of ferroelectrics not only elucidates the electrical dipoles in the unit cells of gems, as shown in Fig. 2, and have been missing pieces in our understanding of the crystalline lattice (Fig. 1). Due to used by artisans and jewellers for decades. phenomena ranging from high temperature interactions between them, these dipoles They have a range of important technical superconductivity to emergent effects

4 CavMag AUGUST 2014 Tony Hewish at 90

Fig. 2. SrTiO3 crystal gems. Above: Tony Hewish with Lord Sainsbury (left) and Humphrey Battcock (right) at the opening of the Battcock Centre for Experimental Astrophysics in October 2013.

This year’s Hewish Lecture was a very special in insulators. It also allows us to think occasion. It was the fifth of the series and about how this can inform developments was timed to coincide with Tony’s 90th in quantum computing and on-chip Birthday. We send Tony our very warmest refrigeration of electronic devices. greetings on this auspicious birthday. This work has significant implications for the collaborative network of theorists and It was an enormous experimentalists within the Cavendish. pleasure to welcome For example, it provides experimental Tony Readhead, examples of the types of phenomena one of Hewish’s most developed theoretically in an early form by distinguished former David Khmelnitskii, while he was working graduate students, in the Soviet Union in the 70’s. Jim Scott’s Robinson Professor canonical understanding of ferroelectrics of Astronomy at the provided basic understanding of California Institute ferroelectric materials for the development of Technology and Director, Owens Valley Fig 3. Calculated and measured of this experimental programme. Radio Observatory, to deliver the lecture phase diagram for quantum on the subject of Back to the Beginning critical ferroelectrics. Collaborations and funding support in Cosmology and Experimental Radio ranging from US, Japan, Kazakhstan, Astronomy. Uzbekistan, Brazil, Greece and Singapore not only made this work possible, but are The discovery of pulsars in 1967 will always also helping expand the scope and broader be associated with the names of Antony utility of these findings. In particular, the Hewish and Jocelyn Bell-Burnell, but the idea of multiferroic quantum criticality, seeds of their achievement were sown where melting of both the spin and the long before [1]. Hewish began his lifelong charge order occur simultaneously, gives involvement in studies of rapidly fluctuating rise to entirely new states of matter. radio signals caused by irregularities in the Intriguingly, the models constructed intervening ionospheric, interplanetary by Rowley and his collaborators and interstellar media in the late 1940s. provide paradigms for developments in These resulted in a series of important fundamental physics through analogies contributions to many different aspects of with phenomena found in particle physics radio astronomical science. The discovery and cosmology. of pulsars was a huge bonus in a sustained Fig 4. Melting of spin and charge campaign of outstanding science. [1] S. E. Rowley, L. J. Spalek, R. P. Smith, M. P. quantum order in the same phase M. Dean, M. Itoh, J. F. Scott, G. G. Lonzarich space - the new scenario of [1] for more details, see: M.S.Longair (2011), and S. S. Saxena, 2014. Ferroelectric Quantum Multiferroic Quantum Criticality. The Discovery of Pulsars and the Aftermath, Criticality, Nature Physics, 10, 367-372. Proc. Amer. Phil. Soc., 155, 147-157. Siddharth Saxena and Stephen Rowley

AUGUST 2014 CavMag 5 Nano-spintronics

Andrew Ferguson, Hitachi Senior Fellow to physics. One solution is to generate a electrons and if they move past electric in the Microelectronic Group, describes magnetic field from a nearby electric current fields in the crystal structure of their wire, some remarkable recent advances in the carrying wire. This applies a torque to the they feel an additional magnetic field. burgeoning field of nanospintronics in magnetisation, causing it to rotate or even Since each electron itself is a tiny magnet his research group. switch. More recently it was discovered they experience a torque, and if the wire that, by passing electricity directly through is a magnetic material, this tiny torque How does electricity affect a magnet? certain magnets, a new type of torque with experienced by each electron affects the So goes one of the questions that is quantum-mechanical and relativistic origins larger-scale magnetisation of the magnet. currently occupying my research group. The could act on the magnetisation. We believe This is the principle behind the spin-orbit interaction of electricity and magnetism is that the physics found in this ‘spin-orbit torque. an important topic in technology, especially torque’ may enable new ways in which to in data storage where nano-scale magnets write information into magnetically stored The spin-orbit torque has been observed store information in hard-drives and are data. The name 'spin-orbit' refers back to at room temperature in layers of magnetic expected to do likewise in emerging atomic physics in which case an electron cobalt with non-magnetic materials such magnetic memories. Perhaps surprisingly, bound by an electrically charged nucleus as tantalum and platinum, materials which given the long history of electromagnetism, feels a component of magnetic field due are suitable for memory devices. However, this question underlies a fast moving area to its orbital angular momentum - it is we work with (Ga,Mn)As, a ferromagnetic of experimental and theoretical physics moving around an electrical charge. This semiconductor which becomes magnetic research. affects the microscopic magnetic moment below about -100 °C, as a model system. of the orbiting electron and causes the fine We believe it is the simplest material in A bar-magnet can be oriented with its structure in atomic spectra. which to study these effects. magnetisation in one of two directions (the magnetisation is a vector that points Special relativity is famously responsible If the magnetisation of a magnet is from the South to North poles) giving the for time-dilation and length contraction. slightly disturbed, it orbits around its magnet the ability to store a single bit of It also mixes up electric and magnetic initial position billions of time each second information. To write that information, fields - if you move past an electric field it before regaining its original position after the magnet could be physically rotated by partially changes into a magnetic field and 10’s of orbits. Our approach to measuring 180 degrees, but since that’s not a scalable vice-versa. This is important in our context the spin-orbit torque is to use microwave solution for data storage we need to turn since electric currents consist of moving frequency electricity to repeatedly apply

6 CavMag AUGUST 2014 Fig. 2.

Fig. 1.

Fig. 1. An electromagnet that has been configured for microwave frequency measurements on magnetic systems at room temperature.

Fig. 2. As microwave frequency electricity is passed through a ferromagnet, a torque is applied to the magnetisation, causing it to orbit its equilibrium position.

Fig. 3. A micrograph showing one of the nanoscale ferromagnetic wires through which an electric current is passed. This one is etched from a crystal of Ga(Mn,As) grown on an epitaxial substrate. Fig. 3.

kicks to the magnetisation at this GHz theorists from NTNU in Trondheim, we [1] D. Fang, H. Kurebayashi, J. Wunderlich, orbiting frequency. In this way, we create started to explore the reciprocal effect of K. Výborný, L. P. Zârbo, R. P. Campion, A. a stable orbit for the magnetisation, the spin-orbit torque, whereby orbiting Casiraghi, B. L. Gallagher, T. Jungwirth allowing us to measure the magnitude magnetisation creates an alternating and A. J. Ferguson (2011) Spin–orbit- and symmetry of the spin-orbit torque [1]. electrical current [3]. It took us about 3 driven ferromagnetic resonance. Nature Further measurements enabled us to find a years to realise the first demonstration of Nanotechnology 6, 413–417. so-called anti-damping contribution to the this physical phenomenon which we refer spin-orbit torque [2]. Together with theorists to as magnonic charge pumping, and it [2] H. Kurebayashi, Jairo Sinova, D. Fang, at the Czech Academy of Sciences and at couldn’t have been achieved without the A. C. Irvine, T. D. Skinner, J. Wunderlich, Johannes Gutenberg University in Mainz innovations of Chiara Ciccarelli, a talented V. Novák, R. P. Campion, B. L. Gallagher, as well as with collaborators at the Hitachi junior research fellow in my group. E. K. Vehstedt, L. P. Zârbo, K. Výborný, A. Cambridge Laboratory and at the University J. Ferguson and T. Jungwirth (2014) An of Nottingham, we understand this effect What does the future hold for us in this antidamping spin–orbit torque originating in terms of the quantum mechanical phase field? As a physicist, I view our job to be from the Berry curvature. Nature accumulated by electrons as they accelerate to investigate new phenomena related Nanotechnology, 9, 211–217. though the material. As its name suggests, to spin-orbit torque, and new materials the anti-damping torque opposes the which display this effect, rather than [3] C. Ciccarelli, K. M. D. Hals, A. C. Irvine, magnetic damping of the magnetisation, V. Novák Y. Tserkovnyak H. Kurebayashi, giving the possibility to create a microwave to engage in technical developments , , A. Brataas and A. J. Ferguson., submitted oscillator with a direct current. towards magnetic memory. Over the next few years we will set up new microwave (2014). Reciprocity appears throughout physics. measurements and collaborate with Members of Andrew Ferguson’s Nanospintronics For example, electricity drives mechanical material growers in Canada, Germany Group include: Dr Chiara Ciccarelli (Junior motion in a motor but the same device and in the UK, using the experimental Research Fellow at Caius College), Dr Nick tools we build to measure new magnetic when driven mechanically creates electricity Lambert (Post-doctoral Research Assistant), and it becomes a dynamo. Reciprocity materials. There are questions that need to Tim Skinner (Ph.D. student), Megan Edwards is relevant to our latest experimental be answered, particularly in more complex (Ph.D. student), Vahe Tshitoyan (Winton Ph.D. advance. After we published our first cases of magnetic metals. No doubt there studentship), Adam Esmail (Ph.D. student) and paper on spin-orbit torque, together with will be a few surprises too. Zhou Fang (Ph.D. student).

AUGUST 2014 CavMag 7 Physics and Industry: Past, Present and Future

Andy Jardine reflects effects. The original work was published have substantial impact. For example, on the long term in the Proceedings of the Royal Society [1] roughly 13.5% of Australia’s final energy impact of basic but, despite the originality of the ideas, it consumption is in mining, and much of theoretical research received little attention. that is associated with the comminution in Condensed of rock, meaning its reduction from one Matter Physics As the importance of adhesive contact in average particle size to a smaller value. and describes technological problems has grown, the innovative research significance of the JKR theory has finally Recent experimental results from the in the Surface, been realised. Fig. 1 shows the history of group have developed a small scale Microstructure and Fracture Group citations of the work. At the present day, physical model of rock fragmentation, (SMF) of immediate interest to industry. when immediate impact is so highly valued, at pressures comparable to those in it is interesting to note that more than 20 a typical borehole. The model has In the Surface, Microstructure and Fracture years of relative obscurity passed before the revealed how increasing the rate of Group, one of the ‘condensed-matter’ true significance and impact emerged. The dynamic loading in a prototypical based groups in the Cavendish, most approach provides a valuable foundation, rock causes the material to fracture research activities focus on different aspects upon which many modern experiments on progressively finer length-scales, of material dynamics. Broadly speaking, are based, including ongoing research eventually reaching the mesoscopic the group works in two major areas – firstly, within the SMF Group. It is clear that grain size of the material. Much of characterising and understanding atomic the combination of fundamental physics the analysis was made possible by scale dynamics at surfaces, including research, with an applied industrial context the combination of analysis facilities adsorption and desorption, quantum motion has stimulated a rather important theory, available within the department and of atoms, and atomic-scale friction; and which after 40 years continues to have an the wider University, as well as the secondly, studying the response of larger increasing impact. comprehensive workshop facilities scale, often meso-structured materials at required for difficult sample preparation. the continuum level – these include pure, Energy Efficiency in the Mining Industry An example of the tomographic composite, granular and even geological reconstruction of rock microstructure is materials. Together, these activities span an Current industrial collaborations in the SMF shown in Fig. 2. unusually wide range of length- and time- group include ongoing projects with the scales, from nanometres and picoseconds mining industry. Primarily, these interactions The results promise to allow the upwards. are focussed on a better understanding efficiency of blasting operations to be

Many of these areas are of direct importance to industry, and the group has a long history of working with industrial organisations. Here, we describe several examples of fundamental research with industrial links, to highlight the impact of past and present industrially collaborative research, as well as looking forward to new challenges in the future.

JKR Adhesion: A longstanding but increasingly important theory

Contact and adhesion between different materials is fundamentally important to any mechanical system, and particularly so in modern advanced material composites. The Fig. 1. Published work referring to the Fig. 2. X-Ray tomographic reconstruction of ‘JKR theory for adhesion’ was developed in original ‘JKR’ paper by Johnson, Kendall and the microstructure of a sample of Gosford Roberts. After a slow initial reception, the Sandstone. The grey regions show the the 1970s by Ken Johnson, Kevin Kendall citation rate began to increase dramatically granular structure, primarily quartz and and Alan Roberts, in a collaboration 20 years after publication (data obtained muscovite, while the dark regions correspond between what was then the Physics and from the Web of Knowledge). to internal void. Chemistry of Solids group, the predecessor to the current SMF group and where Kendall and Roberts obtained their PhDs, the University Engineering Department and the of the mechanisms of rock mechanics, improved, for example, by tuning the rock British Railways technical centre in Derby. with long term aims related to improving blasting process to modify the internal efficiency - other projects have included microstructure and so reducing energy The JKR theory quantifies the energy developing approaches to the removal requirements later down the line. The work balance between surface energies and of lead from mining consumables. The also promises to bridge the mesoscale elastic deformation energies when two elastic spheres are brought into contact. It scale of the mining industry, with a global gap between fundamental simulations allows the contact area to be calculated, market capitalisation of 750+ billion dollars, of material fracture, which can now be which means the theory can be used to means that even small improvements in performed with quantum mechanical interpret a wide range of experiments and efficiency through better understanding precision, and the large scale continuum to study a variety of adhesive and contact of the underlying physical processes, can level simulations widely used in industry.

8 CavMag AUGUST 2014 Richard Hills FRS

Richard Hills, Emeritus Professor of Radio Astronomy, has been elected to Fellowship of the Royal Society.

We are delighted to congratulate Richard Hills on his election to the Royal Society of London. The citation for his election to the Society is as follows: Fig. 3. The first helium atom images obtained using the prototype neutral helium atom microscope. Left: comparison of a TEM grid with optical and neutral helium imaging. Right: Calibration sample of tin spheres on carbon, illustrating the different contrast ‘Since the early 1970s Richard Hills has mechanisms. played a leading role in the development of radio astronomy at millimetre wavelengths, an essential zone of the spectrum for the study of star formation in galaxies. As Project Scientist of the James Clerk Maxwell Telescope on Hawaii he was closely involved with the design and operation of this highly successful telescope. For his outstanding Looking forward: New microscopy The group has recently been awarded contribution to this project he was awarded with neutral helium atoms an EPSRC Impact Acceleration award the Jackson Gwilt Medal and Gift of the to take the project further towards Royal Astronomical Society in 1989. From Most recently, the group is planning to a commercially viable proposition, 2007 to 2012 he was Project Scientist of develop new industrial links through a by dramatically improving both the the Atacama Large Millimetre/Submillimetre completely novel form of microscopy resolution and imaging rates. We have Array (ALMA) in Chile. The first scheduled using neutral helium atoms. Atoms already had interest from the industrial observations at 345 GHz using 16 of offer a quantum probe of a surface microscopy sector, which is actively the planned 66 antennas took place in that is non-destructive, yet potentially following progress with a view to taking September 2011. These demonstrated with higher resolution than optical the work further. To complement the the full angular resolution obtained microscopy. The technology has instrumentation, a new PhD research by phase-coherent aperture synthesis emerged from a combination of helium project beginning in October 2014 which requires continuous monitoring of beam production and measurement will explore the fundamental contrast atmospheric absorption along the line of techniques developed within the group mechanisms in atom based imaging. sight above each antenna. The outstanding over the past 10 years. The group scientific leadership shown by Richard Hills has been able to assemble a low- In summary, the two-way flow of undoubtedly played a major part in the resolution prototype instrument in a new research results between industry and success of this challenging international ‘microscope geometry’ on something academia has proved to be particularly project.’ of a shoestring by re-tasking existing fruitful over many years, and goes equipment. Fig. 3 shows some of the far beyond simply selling university first images obtained, compared with generated Intellectual Property to the Furthermore... highest bidder. With new initiatives such conventional optical images. as the Maxwell centre, we look forward We also congratulate to even greater successes in the future. Peter Littlewood on The technology is particularly exciting his appointment as as we expect new contrast mechanisms [1] K. L. Johnson and K. Kendall and A. the new director of and, perhaps more importantly, the D. Roberts, 1971. Surface energy and the Argonne National energy of neutral helium atoms is the contact of elastic solids, Proceedings Laboratory. Argonne roughly six orders of magnitude lower of the Royal Society of London, A324, has an annual budget than in an electron microscope, meaning 301-313 of $722 million and a that beam-induced sample damage staff of 3350. Peter does not take place and so enables was Head of the experiments on whole new classes of Cavendish from 2005 delicate materials to be carried out. to 2011.

AUGUST 2014 CavMag 9 Rutherford Schools Physics Project - An update

In the July 2013 issue of CavMag, we announced the beginning of an exciting five-year project aimed at developing the skills of 16–19 year old potential physicists, funded by a £7 million grant from the Department for Education. The aim is to provide support and extension materials for students and their teachers across the whole of the UK. Mark Warner and Lisa Jardine- Wright report on progress.

University physics and engineering require students to be fluent in mathematics and in physics problem-solving. Being able to apply physics with the tools of mathematics is a measure of how deeply you understand the subject. Universities want to admit students who are beginning to think like physicists. The most important skill is the ability to deconstruct a problem through sketching diagrams to digest the information within it, assembling ideas from different areas of physics and using mathematical skills to understand the phenomenon quantitatively and symbolically. The Rutherford Schools Physics Project (RSPP) provides extension materials for students aged 16–19 to develop these key skills within areas of the existing A level curriculum, enabling students from all backgrounds to gain expertise beyond school level which will mechanics, and soon will include waves, An example of a half-day event (3 hours) help them to apply for physics, engineering optics and electric and gravitational fields, as would typically include: and mathematics courses at universities well as the mathematics relevant for physics throughout the UK. at this level. Hints for each question, both • 15 min introduction. text and scribble videos, will be available for • 45 min of problem solving (including a Delivery of the RSPP consultation, along with the relevant physics 5 min demonstration). and mathematical concepts linked to each • 15 min break for drinks Hub events are held in partner schools, question. A pilot resource website was • 45 min of problem solving (including a typically a half day, with a theme - for launched towards the end of 2013 and is 5 min demonstration). example, physics and vectors, exponentials, available at http://isaacphysics.com • 50 min lecture (for example, vectors and so on. Organisation and materials and spin) are provided by the RSPP, as well as Getting involved with the project collaborating in the delivery of the material Acting as one of our lead teachers can with our partner teachers. To support Within the project there are opportunities vary in commitment from helping us the teachers’ Continuing Professional for teachers, graduate students and identify a room or rooms in your area and Development (CPD), residential courses for undergraduates to get involved. The RSPP which schools to invite from the locality, them have been held in Cambridge and in wishes to engage with enthusiastic physics to suggesting new topics and developing future these will take place elsewhere. teachers to help the team expand, delivering content and problems in that area. more face-to-face events all around the UK The on-line platform MOOC, standing for students aged 16-19 and their teachers. What is involved? for Massive Open On-line Course, is both A partner school acts as a central location so for student self-directed learning, and as that multiple schools can attend the events. Specifically, what is involved in these events additional materials and lessons directed Typically we deliver two or three, half or one includes: by teachers. Graded problems in 6 levels day events per year in each of our partner spanning the GCSE/AS transition to the school locations, each event focussing on a • Identification of surrounding partner A2/university transition are available in specific topic within the A-level curriculum. schools and teachers to invite to events.

10 CavMag AUGUST 2014 • Liaising with the project’s administrator for students who engage with the problems • Exponentials Partner workshop – 9th to choose suitable dates for events. but who don’t have access to help from a July – Ermysted Grammar School, • Discussion with the project’s physicists physicist teacher. Skipton – AS students about suitable programmes and • Vectors Partner workshop – 9th July – content. Current and Forthcoming Events Southend High School for Boys – AS • Booking a local venue and suitable students room(s). The schools listed here for the partner Upcoming events: • Liaising with the project administrator workshops are kindly acting as hosts for all • Teacher CPD Day – 26th/27th who will publicise the events and surrounding schools. The teacher CPD days September – Venue one of (London, register students. venues are to be confirmed but the dates Cambridge, York, North West) And the option to: are fixed. • Teacher CPD Day – 23rd /24th October– • Create content for new topic Venue one of (London, Cambridge, workshops and events from within the Events already held: York, North West) curriculum. • Exponentials Partner workshop - 24th • Teacher CPD Day – 19th/20th Support is provided by the RSPP team and June – Highgate School, London – AS December – Venue one of (London, there are lots of benefits for you, your students Cambridge, York, North West) students and your school. • Exponentials Partner workshop - 27th • Teacher CPD Day – 13th/14th February June – Netherhall School, Cambridge – 2015 – Venue one of (London, Access to the materials is location- and AS students Cambridge, York, North West) school-independent. The only requirement • Teacher residential 28th-30th June – is access to the internet and so can be Cambridge If you would like to register for one of these accessed from a library, at home, on a • Senior Physics Challenge 30th June -3rd events, or find out further information, mobile on the bus from school and so on. July – AS students – Cambridge or wish to contact the project team, Access does not require input from teachers, • Exponentials Partner workshop – 7th please e-mail the project manager and although of course we positively encourage July – Queen Elizabeth Grammar administrator, Mr David Taylor (dst28@phy. teacher input. There will be project support School, Kent - AS students cam.ac.uk).

AUGUST 2014 CavMag 11 Maxwell, the Ether and the Michelson-Morley Experiment

While studying the papers of James Clerk relative velocity of the ether equal to Maxwell published during his period as that of the earth in its orbit would be Cavendish Professor, I was intrigued by only about one hundredth million part of the title of his last posthumous paper of the whole time of the transmission, and 1880 with the title, On a Possible Mode would therefore be quite insensible.’ of Detecting a Motion of the Solar System through the Luminiferous Ether [1]. The This fractional time difference is just the paper was in fact by George Stokes, square of the aberration, ∆θ ≈ (v/c). reporting a letter which Maxwell sent to Mr. D.P. Todd of the Nautical Almanac Office Albert Michelson recognised that, contrary in Washington dated 19 March 1879. The to Maxwell’s assertion, very small path main body of the letter concerns the use of differences could be detected by optical accurate timing of the eclipses of Jupiter’s interferometry. In his paper on the first satellites as a mean of measuring the speed version of the experiment of 1881 [3], of light plus the Earth’s motion through the Michelson states explicitly that: ether. This required an accurate knowledge of the orbits of Jupiter’s satellites. Maxwell ‘The following is intended to show writes, that, with a wave-length of yellow light as a standard, the quantity [the path ‘I have therefore taken the liberty of difference between the light rays] — if it writing to you, as the matter is beyond exists — is easily measurable.’ the reach of anyone who has not made a special study of the satellites.’ Interestingly, in this paper Michelson carried out the first estimate of the time-delay But, more germane is the remark in an between light propagating parallel and earlier paragraph. perpendicular to the motion of the ether, but made an error in his calculation in which ‘… in the terrestrial methods of the expected difference was overestimated determining the velocity of light, the by a factor of two. This was quickly light comes back along the same path corrected by Alfred Potier and in more detail again, so that the velocity of the earth by Hendrik Lorentz. The result was that with respect to the ether would alter the the 1881 result had lower significance and time of the double passage by a quantity the need for an improved experiment was depending on the square of the ratio of recognised in the introduction to the 1887 the earth’s velocity to that of light, and paper by Michelson and Morley. this is quite too small to be observed.’

This statement is somewhat more specific Fig. 1 shows the much improved than its first appearance, which is in his Michelson-Morley experiment of 1887 [4]. remarkable essay Ether in the great ninth In Michelson’s own words, edition of the Encyclopaedia Britannica [2]. Maxwell contributed regular essays: atoms, ‘… the interferometer was mounted on attraction (1875); capillary action (1876); a block of stone 1.5 m square and 0.25 constitution of bodies, diffusion, diagrams m thick resting on an annular wooden (1877); ether (1878); Faraday (1879). The ring which floated the whole apparatus on mercury.’ ‘It must be concluded that the alphabetical series terminated with his experiment shows no evidence of a death in 1879. The essay is a tour de displacement greater than 0.01 fringe force of simple, logical and clear thinking, The experiment was performed by observing … With v/c = 1/10,000, this gives an in which he established the necessary the movement of the central fringe of the expected displacement of 0.4 fringes. physical properties of the ether, given the interferometer as the apparatus was rotated The actual value is certainly less than known facts of the modes of propagation ‘fairly uniformly and continuously’ through and polarisation of light. The question of 360° and measurements made every one- one-twentieth of this actual amount and determining the Earths’ motion through sixteenth of a revolution. In Fig. 2, the probably less than one-fortieth.’ the ether is discussed, his preference being mean displacements of the central fringe for ‘one-way’ tests using the eclipses of the during rotation through 360° are compared The statistical significance of the null-result satellites of Jupiter as the best stable clocks with the expected sinusoidal variation was quite enormous. The experiment was available. In an earlier paragraph, he wrote if the Earth moved through a stationary repeated at different times of the year by about the terrestrial tests: ether at 30 km s-1, the dotted sinusoidal Morley and Miller, in case the motion of line corresponding to only one eighth of the Earth about the Sun was cancelled out ‘… the increase of this time (of the the theoretical displacement. Again, in by the drift of the ether, but the same null double journey) on account of the Michelson's words, result was found.

12 CavMag AUGUST 2014 Fig. 1. Left: The mounting of the Michelson-Morley experiment. Right: the reflections involved in the interferometer [4].

Fig. 2. The null result of the Michelson-Morley experiment [4]. The solid line shows the average movement of the central fringe as the apparatus was rotated through 360°. The dotted line shows one eighth of the expected sinusoidal variation if the Earth moves through the stationary ether at 30 km s-1.

Centre: Portrait of James Clerk Maxwell by his cousin Jemina Blackburn (née Wedderburn). © Cavendish Laboratory.

In the 1962 reprint of Michelson's book that there is no explicit reference to the [2] Maxwell, J.C., (1878). Ether, Studies in Optics, Harvey B. Lemon wrote in Michelson-Morley experiment in Einstein's Encyclopaedia Britannica, Ninth edition, 8, his introduction: great paper of 1905 on the Special Theory 568-572. of Relativity - Michelson's null result instantly ‘To the complete astonishment and became one of the established facts in the [3] Michelson, A. A. (1881). The Relative mystification of the scientific world thorny problem of understanding the nature Motion of the Earth and the Luminiferous this refined experiment also yielded of the ether. Evidently, Maxwell’s words had Ether, American Journal of Science, 22, absolutely negative results. Again must stimulated Michelson to carry out one of the 120-129. we note at this point the universal great experiments of physics. [4] Michelson, A. A. and Morley, E.W. confidence with which any experimental (1887). On the Relative Motion of the fact announced by Michelson was [1] Maxwell, J.C., (1880). On a Possible Earth and the Luminiferous Ether, American instantly accepted. Not for twenty Mode of Detecting a Motion of the Solar Journal of Science, 34, 333-345. years did anyone have the temerity to System through the Luminiferous Ether, challenge his conclusion.’ Proceedings of the Royal Society of London, Malcolm Longair 30, 109—110. This may well be part of the reason

AUGUST 2014 CavMag 13 Upcoming changes to the Physics curriculum

The government has New projects for the held around the country including here at recently announced the Cavendish Laboratory. reforms to the Outreach Team current GCSE and A Stimulating Physics Network level qualifications. The department has recently received programme extended after boost in With these additional funding for a set of new and funding modifications the exciting outreach projects. The funding will former Secretary of be used specifically to implement strategies The IoP has received £4.3 million in funding State for Education, to encourage more girls into physics. A to continue its Stimulating Physics Network Michael Gove, aims new series of school workshops has been programme. The new funding will allow to reduce grade planned that will build upon the success of the Institute to continue supporting inflation, introduce more rigorous previous workshops and will also allow more physics teachers and will also finance two direct provision for girls. The workshops content and stretch the more able new initiatives called Improving Gender will run during the school holidays with students. These provide the outreach Balance and the Maths & Physics Chairs the hope that parents will accompany team with new challenges. scheme. The first will be a pilot project students and thus also gain an awareness that aims to identify and then overcome of both physics and the University. There These changes come about after a lengthy the factors that are currently discouraging will be sessions dedicated exclusively to girls consultation process, which involved both girls from studying physics at A-Level. The based on topics that they find particularly schools and universities, and which led to a second scheme will recruit top PhD students interesting. series of recommendations. into physics teaching with a tempting benefits package. A pilot project will also be started that A level Physics will be first to be given a aims to identify the different attitudes shake-up, the new proposals coming into of girls and boys to physics. Students Forthcoming Events at the effect in September 2015. The course will at participating schools will be sent a include the introduction of 12 assessed Cavendish 'toolkit' and asked to complete a practical pieces of practical work which will be a task. Some students will have prescriptive requirement for A level Physics. At the end Physics at Work manuals whilst others will only have minimal of the year, students will receive either a instruction. A questionnaire will accompany pass or fail grade for these practicals as The 30th Physics at Work exhibition will be the toolkit and will be used to help assess well as a tiered grade for their written taking place from Tuesday 23rd September the different techniques used by different examinations. This proposal responds to 2014 - Thursday 25th September 2014 genders alongside differences in beliefs and here at the Cavendish Laboratory. The concerns from the university sector that confidence. students are entering higher education event will see research groups from across without the necessary experimental skills. the department come together with their Otherwise, the content of the Physics A level Outreach News from the counterparts from industry to showcase the course will not see any major overhauls. Institute of Physics application of Physics within the working- There will however be greater emphasis on world. Unfortunately Physics at Work mathematical skills, especially the concepts New 'opening doors' project to address 2014 is now fully booked. Please email underlying calculus. This mirrors a general gender imbalance in Physics [email protected] to be added to trend to increase the level of mathematical the waiting list for places. awareness within all the sciences. A pilot project called Opening Doors has been initiated at the IoP. The project, funded Cambridge Physics Centre Lectures The overall structure of A levels will also by the Government Equalities Office, will change with the decoupling of the A level seek to eradicate gender stereotypes that A new series of CPC lectures has been and AS level examinations. These two are detrimental to the uptake of A-level confirmed for the beginning of the next qualifications will become stand-alone physics amongst girls. It will build upon academic year. The lectures take place at courses, rather than one as part of the previous work carried out under similar 6pm in the Pippard Lecture Theatre and are other. The exams will be sequential with schemes such as the IoP Juno project that free to attend! students sitting one examination at the end concentrated upon the under-representation of the AS level year and one examination at of women within university Physics Tuesday 14th October 2014 the end of the two years of study for the A departments. Physics of Juggling – Dr Colin Wright level qualification. 3-minute wonder winner announced Thursday 13th November 2014 GCSE's will not change until September Relativity - understanding the 2016 and consultations are still in progress. This May, the final of the IoP's 3-minute connection between space and time It is however apparent from preliminary wonder competition was held in the Faraday Dr Julia Riley considerations that the new science GCSEs Theatre at the Royal Institution in London. will require much more scientific knowledge Hannah Wakeford from the University of Tuesday 2nd December 2014 and detail with clearer mathematical Exeter took home the top prize of £500 Can science make a cyclist faster? requirements for each topic. Additional for her 3-minute explanation of how to Professor Tony Purnell content will include nanoparticles and space search for water in the atmosphere of other physics. planets. Regional finals had previously been Lizzie Bateman

14 CavMag AUGUST 2014 Keeping the show on the road

With approximately 1000 people working on site and about 850 Laboratory. The team are also particularly popular since a number of undergraduates passing through the Laboratory each term, it is a them supervise the wine and canapé receptions after lectures to the major challenge to keep everything up to the standards expected Cavendish Physical Society and the Scott Lectures. of one of the largest physics departments in the country.

This is where the ‘behind the scenes’ support staff who do all the really physical hard work of implementing all the changes and keeping the Laboratory in its ‘ideal normal’ state come in. We have been very lucky to have an excellent staff of cleaners and maintenance crew. They have been particularly busy with all the changes which have taken place with the move of the Astrophysics Group to the Battcock Centre and the consequent ‘musical chairs’ as groups move from one location to another. The same process will continue with the construction of the Maxwell centre and ultimately the planned move of the rest of the Laboratory to the Paddocks site.

The Maintenance Team: Back row from left: Graham Cox, Nigel Dibden, Jeff Catlin, Graham Matthews. Front row from left: Mark Callaghan, Keith Matthews, Alan Turner, Dave Smith.

The maintenance staff have a huge operation to maintain. The fact that every area of the Laboratory has been refurbished so many times brings new maintenance challenges, and these are particularly demanding with the requirements of current Health and Safety legislation. Keith Matthews looks after the team who have to combine installing new equipment, services, furniture, and so on as well as dealing with the constant flow of requests for the repair and maintenance of all types of existing equipment and facilities. They have been able to take on important projects for the Laboratory because The Cleaning Team. Back row from left: Mark Threadgold, Gleb Tsumak, Algirdas Zilevicius, Zina Manekiene. Front row from left: Monika most of them have been here for a considerable time and have in- Nierodzinska, Marzena Kulma, David Rudderham, Liucija Zileviene, depth knowledge of the place. We are one of the few departments Xiuping Zhang. in the University who have delegated powers to refurbish and maintain our own buildings. This is mainly due to the expertise of our David Rudderham supervises the work of all the cleaning staff and, as Maintenance team and their commitment to looking after our ageing can be seen from the names of the excellent team, it is like managing buildings. a little United Nations. It is a great tribute to the team that, despite the constant comings and goings throughout the buildings, the Laboratory The efforts of both these teams are essential to the operations of the always looks well presented, particularly in the public areas where Laboratory and we owe them all a great debt of gratitude for their our prominent visitors and guests gain their initial impressions of the sterling efforts.

If you would like to discuss how you might contribute to the Cavendish’s Development How you can contribute Programme, please contact either Professor Malcolm Longair ([email protected]) or Professor Andy Parker ([email protected]), who will be very pleased to talk to you confidentially.

»» Online Giving If you wish to support our outreach activities, please through the provision of a legacy in one’s will. This go to: has the beneficial effect that legacies are exempt The University’s Office for Development and Alumni from tax and so reduce liability for inheritance tax. Relations has made it easier to make donations campaign.cam.ac.uk/giving/physics/outreach The University provides advice about how legacies online to the Department and to two of our special can be written into one’s will. Go to: campaign. programmes. If you wish to make a donation to the If you would like your gift to be applied to cam.ac.uk/how-to-give and at the bottom of the Department, please go to: some other specific aspect of the Development page there is a pdf file entitled A Gift in Your Will. Programme, please contact Andy Parker or Malcolm It is important that, if you wish to support campaign.cam.ac.uk/giving/physics Longair. The Development portfolio is at: the Cavendish, or some specific aspect of our www.phy.cam.ac.uk/development development programme, your intentions should If you wish to support the graduate student be spelled out explicitly in your will. We can suggest programme, please go to: »» A Gift in Your Will suitable forms of words to match your intentions. Please contact either Professor Malcolm Longair campaign.cam.ac.uk/giving/physics/ One very effective way of contributing to the long- ([email protected]) or Mr Robert Hay (rach2@ graduatesupport term development of the Laboratory’s programme is cam.ac.uk) who can provide confidential advice.

AUGUST 2014 CavMag 15 News

2014 Institute of Physics medals and prizes: many congratulations to

Franklin Medal and Prize Paterson Medal and Prize Swan Medal and prize Professor Ben Simons Dr Sarah Bohndiek Professor Mike Payne For the application of For her remarkable For the development of non-equilibrium statistical work in developing computational techniques mechanics to provide advanced molecular that have revolutionised fundamental new insights imaging techniques and materials design and into the mechanisms applying them to address facilitated the industrial that regulate stem cell questions at the interface application of quantum behaviour in tissue of physics, biology and mechanical simulations. maintenance and disease. medicine.

Personal Promotions New Appointments Suchitra on her Soapbox

Many congratulations to We welcome the following new members of the Recently Suchitra Sebastian (on the left) took our new Professors, Department: part in an outreach event on the South Bank in Crispin Barnes (left), London which involved female scientists getting Russell Cowburn Prof Pavlos Savvidis: Leverhulme Trust Visiting on their soapboxes and talking about their (below left) and Zoran Professor, Nanophotonics research to passersby. She writes: ‘It’s really an Hadzibabic (below right). Juan Benayas Sanchez: Facilities Manager, awesome event! We should encourage more Semiconductor Physics Cavendish members to participate.’ Please Christopher Darvill: Instrument Maker consider getting on your own soapbox. Matthew Pluck: Instrument Maker David Smith: Plumber Linda Whyles: Project Coordinator, TFM, formerly in SMF Leavers

We wish the following all best wishes in their next roles:

Sarah Adderley: PA to Prof Athene Donald, Alfonso Fernandez-Montenegro: Cook (Maternity Cover) Julie Kite: Project Coordinator, TFM Kavitha Nimaladevi: Assistant, HEP Likewise, congratulations to our newly promoted Readers, Ben Gripaios and Austen Lamacraft. Success for Jan Merens

The Parliamentary and Scientific Committee runs the SET for BRITAIN event in collaboration with seven scientific societies including the IoP and with private sector and institutional sponsorship. The winner of this year’s Silver Medal and £2,000 was Jan Mertens, a PhD student in the NanoPhotonics Group of the Cavendish Laboratory. His research involves squeezing light into tiny gaps to produce powerful sensors.

Contacts

The Cavendish Laboratory Tel: +44(0) 1223 337200 Head of Department Director of Development JJ Thomson Avenue Fax: +44(0) 1223 363263 Professor Andy Parker Professor Malcolm Longair Cambridge Email: [email protected] Tel: +44 (0)01223 337429 Tel: +44 (0)1223 765953 CB3 0HE www.phy.cam.ac.uk Email: [email protected] Email: [email protected]