Superfluid gases near absolute zero temperature
Wolfgang Ketterle, Massachusetts Institute of Technology
What is the benefit of realizing superfluidity in a gas a million times more dilute than air? Such systems consist of well-separated atoms which can be observed and manipulated with the control and precision of atomic physics, and which can be treated with first-principles calculations. One such form of superfluidity occurs when a gas of bosons undergoes Bose-Einstein condensation (BEC). A richer situation is realized with ultracold fermions. Fermions have to form pairs before they can become superfluid. By continuously changing the interaction strength using a scattering resonance we were able to study superfluidity for varying pair size, connecting the BEC limit with the case of BCS Cooper pairs, which are larger than the interatomic spacing. These studies illustrate a new approach to condensed-matter physics where many-body Hamiltonians are realized in dilute atomic gases.