Concepts and Discovery in Quantum Matter IN CELEBRATION OF GIL LONZARICH’S SEVENTIETH 12–15 July Cambridge, UK Organising Committee Siân Dutton, Malte Grosche, Montu Saxena, Suchitra Sebastian, Mike Sutherland. Thanks to Helen Verrechia, the team of volunteers, and the Department of Physics. Introduction Samuel Johnson once said Curiosity is, in great and generous minds, the first passion and the last. These words could have been written about Gil Lonzarich, one of the most distinguished physicists of his generation. His science has not been driven by an attempt to capture nature in neat equations, but by an exploration of what is possible in systems which have never been looked at before, and which defy conventional explanations. From his early work on superfluidity, through his famous discoveries in superconductivity, to his most recent work on unconventional metallic states, he has always been curious to see beyond what was known. In order to do so, he has developed experimental techniques which have allowed him to study and control the electronic properties of materials in extremely high magnetic fields and at very low temperatures. This work has opened up our knowledge of the quantum universe in complex systems, offering the prospect of completely novel technologies. His list of honours and awards, from his election as a Fellow of the Royal Society, to the most recent award of the Kamerlingh Onnes Prize in 2015, show that he is regarded as a great mind. But, perhaps more importantly, he is also possessed of a generous mind. When not actually standing next to his latest experiment, he can be found in deep conversation with his colleagues and students, not propounding his view, but freely offering his knowledge and experience and listening carefully to others. It is no surprise that he is held in great affection by all who have worked with him. The Cavendish Laboratory is one of the world’s most renowned Physics Departments. It does not retain this position by virtue of its historical discoveries, nor by its modern facilities: it does so because it can still attract the best minds, young and old, to come together in an environment where they can flourish. Gil’s contribution to the life of the laboratory has been crucial for almost 40 years. His passion for his work still burns bright, and, as we celebrate his 70th birthday, long may it continue! Andy Parker is Head of the Department of Physics, University of Cambridge. He has been a colleague of Gil for several years. 3 Editorial he idea of a souvenir book for Gil’s 70th celebration has evolved. From Tthe first tentative idea of a few reminiscences as part of the abstract book, it has grown into an amazing collection of Gil anecdotes – alternately touching, inspiring, humorous – all California at Berkeley as a Regents’ Scholar heartfelt. Such is the warmth Gil inspires, from 1963 to 1967. In this period he a testament to the time and care he met Gerie who became his partner and pours into his multitude of students friend, developed a passion for sports and collaborators. In the process of (playing on the University soccer team), compiling the souvenir book, we have and between his studies worked part been overwhelmed by the memories time at a communication station on an of Gil that poured in, and struck by the uninhabited Pacific Island where he had sentiment expressed that it is a privilege the unforgettable experience of seeing to be able to say thank you. We would like nature untouched by man. to thank all those who contributed, your generosity is much appreciated. In 1967 Gil and Gerie married and moved to the University of Minnesota Suchitra Sebastian and Siân Dutton, in Minneapolis with the support of a Quantum Matter Group Corporate Fellowship. Gil’s research project with W. Zimmermann and L. A word from Gerie Nosanow involved an experimental study of superfluidity in 3He–4He mixtures. il was born in 1945 to Italian The long-term goal was to test the then parents on the Istrian peninsula, sensational prediction that superfluidity Ga small territory that has changed would survive in pure liquid 3He (a Fermi sovereignty numerous times and is now a rather than Bose liquid), albeit under part of Croatia. extreme conditions not yet readily available at that time. Shortly after the end of the second- world war his family moved to northern In 1969 with the support of a Killam Italy and Gil remembers growing up on Fellowship, Gil moved on from the field a beautiful farm bordered by streams of quantum liquids to that of interacting and an ancient castle (said to have been electron systems at the University of occupied by some of Attila’s hordes at the British Columbia in the beautiful city of end of the Classical Roman period). Vancouver. Gil’s PhD project with Andrew Gold aimed at understanding the factors Gil continued his education in America that determine the Curie temperature in where he attended the University of itinerant-electron ferromagnets such as 4 Soon after the completion of his PhD studies Gil took up a one-year post- doctoral position in Cambridge where he had the opportunity to work with David Shoenberg and Brian Pippard. Though Gil and Gerie had only thought to have a grand adventure for a year in Europe, they ended up living in Cambridge longer than they had lived anywhere else. It turned out that Cambridge was meant to be the destiny location – the place where Gil had the opportunity, freedom, support and intellectual environment to explore and develop the problems that fascinated him. This included the development of the technique for the study of quantum oscillatory phenomena in complex materials (beyond the elemental metals of main interest at that time), the use of inelastic neutron scattering to detect paramagnons (dissipative spin fluctuations), the study of the effects of THE “DIARY”. Here, on the right, is the special helium liquefier, designed by Kapitsa, which is of enormous paramagnons on thermal properties and value to the laboratory. Simply and effectively it on electron-electron pairing instabilities, produces supplies of the evanescent liquid gas - the investigation of quantum critical “like milk from a cow” say the researchers. Frank phenomena, and the search for new Sadler, laboratory assistant, makes it, sees enough is always on hand, watches carefully against waste. quantum states in high purity materials. The laboratory is expected to get by for ten years on its current stock of helium, which is a gift from the Canadian National Research Council. Frank Sadler with Pyotr Kapitsa’s helium liquefier and its original description in the Cavendish diary, 1937. Fe, Co and Ni. This programme started with a new kind of experimental test of the applicability of Stoner’s theory and culminated some years later with the first formulation of a realistic expression for the Curie temperature for a ferromagnetic metal (in the limit where the exchange splitting is small compared to the Fermi Above and top left: Gil and Gerie soon after energy). they met in Berkeley, 1966. 5 Gil has been a member of both the the chance to work with one such Cavendish Laboratory and Trinity College hero, namely Frank Sadler, who was as a demonstrator, lecturer, reader very proud of having been Rutherford’s and professor of physics. He is deeply personal technician. He told me many honoured to have been elected a Fellow stories about the old Cavendish Lab. His of the Royal Society of London and the favourite story was of the day when he Institute of Physics, and to have been walked into one of the labs to find JJ awarded the Europhysics (Hewlett- Thomson, Ernest Rutherford and Piotr Packard) Prize for Experimental Physics Kapitza, each in their normal business 1989 (shared with H. Ott and F. Steglich), suit attire, kneeling on the floor with the Max Born Prize and Medal 1991, the their heads close to the ground. They Guthrie Medal 2007, the Rumford Medal were surrounding Kapitza’s novel 2010 and the Kamerlingh Onnes Prize helium liquefier that had recently been 2015. completed, struggling to catch a glimpse of the first drops of the precious liquid. His greatest privilege is to have had the This marked the beginning of research opportunity to work with amazingly in condensed matter physics in the talented students and colleagues from all Cavendish laboratory and led to many over the world, who have taught him at advances over the years. One of these least as much as he has taught them. was the demonstration that the droplets Gerie Lonzarich was born in the State of that these great men were trying to see Utah in 1946, grew up in Southern California would at slightly lower temperatures and studied engineering and fine arts at condense into a superfluid state. the Universities of California at Berkeley and Minnesota at Minneapolis. She met and married Gil in Berkeley during the turbulent, but exciting, I have always been grateful to Gordon 1960s. Among her many activities she was a Squires for introducing me to the field founding member of Cambridge Energy Research of neutron scattering and making it and an administrator for the Quantum Matter possible for me to work at the Harwell Group at the Cavendish Laboratory. Nuclear Reactor to search for the elusive ‘paramagnons’. This required the A word from Gil modification of some of the existing apparatus and the technicians went ere I would like to recall some out of their way to help. One day I stories that involved researchers requested a long tube of ‘aluminum’. The Hin the Cavendish Laboratory in an procurement officer looked at me with earlier era, whom I met during my first surprise, but said ‘come back in three few years in Cambridge.