Bose Einstein condensate: "an exotic fifth state of matter"

The Bose-Einstein condensate is a super-cooled state of matter in which all the atoms have the same energy and quantum characteristics, similar to the way all photons in a laser share the same quantum state. This new form of matter was first predicted mathematically by Indian physicist Satyendra Nath Bose and Albert Einstein in 1924.

The first observation of a Bose Einstein condensate has been obtained in 1995, thanks to the cooling of atom vapors to incredibly low temperatures. This allowed Eric Cornell, Wolfgang Ketterle and Carl Wieman to be awarded the Nobel Prize in 2001.

Physicists are seaking Bose Einstein condensates of particles in solids, because such condensates should show very interesting properties such as superfluidity and superconductivity. A number of claims for BEC have been made using different particles called excitons, magnons, polaritons.

Announcement

Bose Einstein condensation in diluted atomic gases and in condensed matter

The intriguing physics of quantum fluids and the successful observation of the spectacular phenomenon of Bose-Einstein Condensation (BEC) in cold atom vapors, were the main motivation for awarding three Nobel prizes in Physics in 1997, 2001, and 2003. Since 1995, the research on BEC has seen a wide expansion, and has led to major improvements of our understanding of the behavior of highly degenerate Bose and Fermi gases at very low temperature. As a parallel but nonetheless fascinating field of research, the quest for BEC in condensed matter systems has made significant progress since the very first suggestion, by Moskalenko and Blatt in 1962, that a bound electron-hole pair in a semiconductor - an exciton - behaves as a boson and a gas of excitons is expected to undergo BEC under appropriate conditions. Apart from excitons, other kinds of excitations in solids have been proposed as possible candidates for BEC, including quantum Hall bilayers and magnons. Despite these efforts, however, the research on condensed matter BEC was slowed down by the much more complex behavior of electronic and magnetic excitations as well as by the intrinsic technological difficulty in achieving sufficiently low temperatures in a solid. Other limitations come from the finite lifetime of Bose excitations in a solid (contrarily to the virtually infinite lifetime of an atom as a single particle), implying deviations from thermal equilibrium, and from the inherent inhomogeneities of solid materials that lift translational invariance and thus momentum conservation.

Recently, several reports of BEC in the solid sate have been published, including BEC of indirect excitons in double quantum wells, and BEC of polaritons in a semiconductor microcavity. These reports have created a lot of interest within the scientific community and among non scientists. The experiments still leave many open questions as on the nature of BEC and of the quantum fluid, and the observations in different systems have not been fully reconciled with each other. With the 2008 Latsis Symposium, we wish to establish a link between the solid-state and cold-atom communities. The former has access to a new class of solid-state systems whose quantum-fluid behaviour can be probed by simple optical means, at high temperature and lower dimensionality. The latter has developed a vast and deep knowledge in the behaviour of quantum degenerate gases. Over the last ten years, those two communities had little exchange. Close contacts between those two areas would be highly beneficial to both fields and would provide new and deeper insight into the physics of quantum fluids.