Superfluidity, phase coherence and the new Bose-condensed alkali
The phenomenon of superfluidity was discovered in liquid helium nearly sixty years ago, and ever since, following the almost immediate suggestion of Fritz London, it has been the almost universal belief in the condensed-matter community that it is due to the onset of the phenomenon of Bose-Einstein condensation which is theoretically predicted to occur in that system at sufficiently low temperature. However, for various practical reasons, it is extremely difficult even to establish unambiguously that BEC is occurring in 4- He, let alone to test directly some of the ideas which connect it to superfluidity. The recent attainment of BEC in dilute atomic alkali gases opens a new arena in this respect, allowing us to do many experiments which we would have loved to do in 4-He but which are in practice unfeasible in that system. In this talk I first review briefly the fundamental ideas developed in the helium context, then give a general introduction to the physics of the BEC alkali gases, and finally discuss some of the novel possibilities they open up, both already realized and still on the drawing-board.
Professor Anthony J. Leggett, a faculty member of the University of Illinois at Urbana-Champaign since 1983, is widely recognized as a world leader in the theory of low-temperature physics. He was awarded the Nobel Prize in Physics in 2003 (jointly with Alexei A. Abrikosov and Vitaly L. Ginzburg) for his pioneering work on superfluidity.
Anthony Leggett has shaped the theoretical understanding of normal and superfluid helium liquids and other strongly coupled superfluids. He set directions for research in the quantum physics of macroscopic dissipative systems and use of condensed systems to test the foundations of quantum mechanics. His research interests lie mainly within the fields of theoretical condensed matter physics and the foundations of quantum mechanics. He has been particularly interested in the possibility of using special condensed-matter systems, such as Josephson devices, to test the validity of the extrapolation of the quantum formalism to the macroscopic level; this interest has led to a considerable amount of technical work on the application of quantum mechanics to collective variables and in particular on ways of incorporating dissipation into the calculations. He is also interested in the theory of superfluid liquid 3He, especially under extreme nonequilibrium conditions, in high-temperature superconductivity, and in the newly realized system of Bose-condensed atomic gases.
Room 348 / 349 - Arnold Sommerfeld Centre for theoretical Physics - Theresienstr. 37 / III - 80333 Muenchen