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DSM - DRECAM Service De Physique De L'etat Condensé FR9900327 Service de Physique de l'Etat Condensé &' >&«^™- tt Scientific - DSM - DRECAM Service de Physique de l'Etat Condensé Scientific Report 1996-1997 CEA - DSM - DRECAM CEA Saclay 91191 Gif sur Yvette France Front cover : Photomontage containing a turbulent spot in a plane Couette flow, an Hg-1201 crystal, an aluminium bridge to achieve nanocontacts, a dilution refrigerator, and the prototype of the ionisation-heat detector for the Edelweiss experiment. Foreword Understanding the fundamental mechanisms and properties of condensed matter remains an exciting challenge for physicists. It is also a basic requirement for new technological applications, in view of the continued need in all technical domains for ever more elaborate materials and specifically designed devices. The properties of well organized crystals can now mostly be accounted for, but the behavior of less symmetric systems is far from being known. How do, for instance, disordered systems organize and how do they behave ? What are the ultimate electronic or magnetic properties of ultra small devices ? How can one account for strong correlations in many body systems ? These are some of the important questions which arise when the number of relevant parameters can not be reduced by symmetry arguments. The presently available experimental techniques in nanotechnologies and the ever increasing capacity of computers provide a new basis to cope with these problems. The scientific program of the laboratory is centered on these basic interrogations and has already yielded significant contributions. During the last two years described in this report, the laboratory has been at the origin of many crucial advances. Among these, I would like to mention two special highlights which have been widely acknowledged by the scientific community. The first concerns the observation of the spontaneous circulation of superfluid helium due to the rotation of the earth, the second is a demonstration of the existence of quasi-particles of fractional charge in two dimensional electron systems submitted to large magnetic fields. Many of these successes were made possible through close collaborations with other laboratories. From the publications listed in the present report, it can be seen that much of the work has been done in close relationship with other national (principally CEA, CNRS and University) or international laboratories. Such collaborations are essential for the quality of the research. They allow for more elaborate experiments by adding up the specific competencies of different groups. They avoid duplication and help crosscheck results by complementary measurements. In this regard, the importance of the existence of independent but collaborating laboratories should be stressed. The laboratory has tightened its connections with the universities on the conviction that it is not only important for the quality of research but also that it has an important role to play in the educational process. Many physicists take an active part in teaching and all groups regularly receive students from the universities either as graduate or PhD students. This is of vital importance for the laboratory. Fundamental research is a natural extension of academic education and the presence of PhD students maintains this link. They acquire a new experience at the limit of accepted knowledge and they get a practical idea of experiments and critical analysis of data. It is to be hoped that the laboratory will be able to maintain the present number of PhD students in the future. The agreements which have recently been signed between most of the Universities and the CEA should help promote these collaborations. Over the past few years, the activity of our laboratory was formally included in a research program on condensed matter named « Order and Chaos » tcgether with the SPSMS (DRFMC, Grenoble), and partly the SPhT and the LLB. Very fruitful collaborations have long been established between these laboratories but the existence of an official bond was very helpful. It is to be hoped that the general content of this program will continue to be supported by our Institute as the need for fundamental knowledge in condensed matter remains as important as ever. Most of our subjects are related in some way to problems encountered in applied research and our laboratory has always had collaborations with certain applied laboratories of the CEA. However, in fundamental research, many different directions must always be explored in order to reach a global view of the problems and to be aware of the limits of validity of the models. In contrast, in applied research, dramatic choices must be taken in order to launch promising new techniques. The emphasis given to different subjects in pure and applied research programs can never coincide, but closer relationship should indeed be possible. It would probably be helpful if PhD students trained in fundamental physics had better access to positions in applied areas. The ambition of our laboratory is to remain at the top level in its activity of fundamental research in condensed matter physics, in close collaboration with the university and the CNRS, and in connection with the other research activities at the CEA. I hope that the reader will be convinced of the quality of the work reported herein and of the perspectives that it opens. I would like to thank all the staff, visitors and students of the laboratory for their constant efforts to improve the quality of the scientific activity and, more generally, the quality of life in our laboratory. Special thanks are due to all those who have contributed to this report and particularly to Louis Laurent for the intense and very effective work he did to bring together all the documents and prepare the report for publication. J.M. Hammann How to read this report ? A general introduction gives a summary of the present scientific program of the SPEC and presents some of the recent highlights, the organization, the recent evolution and the relationship of the laboratory with the CEA and the scientific community. Most of the information on the organization is gathered at the end of the report in a section called "Facts and Figures" page 233. The central part consists in 20 chapters which can be divided in 4 subsets corresponding to the contributions of the four laboratories of the SPEC. In front of each of these subsets, an inset gives a summary of the respective contributions. The distribution is as follows : Chapter 1- 4 : Soft matter, interfaces and turbulence ; Summary on page 15 Chapter 5 - 11 : Solid state and novel materials ; Summary on page 59 Chapter 12 -16 : Quantum condensed matter ; Summary on page 129 Chapter 17 - 20 : Condensed matter theory ; Summary on page 193 The headings of each chapter list the physicists, technicians, PhD students as well as the visitors and main collaborators which have taken part in the corresponding activities. In most cases, graduate students were involved in some of the work during their training period. Their names can be found in the section Facts and Figures (subsection Teaching and Training). The Index (page 229) lists all the contributors and gives the page numbers at which their names appear. As a reminder, it should be noted that the bibliography of all the physicists of the SPEC can be found on the Internet site: www-drecam.cea.fr/drecam/drecam.french/spec.htm Contents 1 Soft condensed matter and interfaces 17 1.1 Wetting 17 1.1.1 Study of the critical adsorption by neutron reflection ... 17 1.1.2 Wetting films of liquid crystals 19 1.2 Fluctuations and elasticity of liquid surfaces and amphiphilic films 20 1.2.1 Bare water free surface 22 1.2.2 Elasticity of surfactant monolayers 23 1.3 Polyelectrolytes at interfaces 24 1.3.1 Adsorption of charged diblock copolymers at a free surface 25 1.3.2 Existence and structure of charged copolymer micelles . 25 1.3.3 Interactions in concentrated micellar solutions 26 1.4 New directions 28 1.4.1 Liquid-liquid and liquid-solid interfaces 28 1.4.2 Nanodroplets 28 1.4.3 Towards a more quantative understanding of chains at in- terfaces; molecular architecture, new experimental tech- niques and numerical simulations 29 2 Physics of black films 33 2.1 Structure and Interactions in black films 34 2.1.1 A first application: evidence of hydration effects in elec- trolytic black films 34 2.1.2 In-plane order in Newton black films 35 2.2 Complex black films 37 2.2.1 Polymer-surfactant interaction in black films and mono- layers 37 2.2.2 Free standing films of long associating polymers 37 2.3 Perspectives: The two dimensional confinement of biological mole- cules 38 3 Critical phenomena in strongly associated fluids 41 3.1 Ionic Fluids 41 3.2 Supercritical water 42 3.3 Other research activities 43 3.4 Perspective 45 4 Instability and turbulence 47 4.1 Non linear waves 48 4.1.1 One dimensional hydrothermal waves 48 4.1.2 Related experiments 49 4.2 Coupled oscillators 50 4.2.1 Different experimental systems 50 4.2.2 Lattice of coupled instable jets 50 4.3 Subcritical transition to turbulence 51 4.3.1 The plane Couette flow (PCF) case 51 4.3.2 Streamwise vortices as finite amplitude solutions 52 4.3.3 Intermittency in a locally forced PCF 52 4.3.4 Spatiotemporal intermittency 53 4.4 New trends 54 4.4.1 Dynamo effect 54 4.4.2 Granular matter 55 5 Dynamics of disordered and glassy systems 61 5.1 Nanometric particles in the low temperature limit 61 5.1.1 Magnetic characterization of the barrier distribution ... 62 5.1.2 A new relaxation procedure 62 5.1.3 Thermal or quantum dynamics ? 64 5.1.4 Superparamagnetism 65 5.2 Slow dynamics and aging in spin glasses 66 5.2.1 Stationary and non-stationary dynamics 66 5.2.2 Hierarchical barrier model 67 5.2.3 Memory and chaos effects 67 5.3 Glassy behavior of the granular superconductor Lai.sSro.2Cu04.
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