European physical society newsletter

Abstract

We present a brief overview on the history of superfluidity, one of the most remarkable macroscopic manifestations of quantum physics. Special emphasis is on superfluidity in ultracold atomic gases. The discovery and earliest study of superfluidity is associated with Allen, Misener, Kapitza, London, Tisza, and Landau (late 1930s, 1940s). The liquid helium superfluid transition was first observed by Kamerling–Onnes on April 8, 1911. Keesom had discovered the “lambda-transition” in He-4 in 1932. Landau associated superfluidity to the existence of a “critical velocity” for an object moving through a superfluid. Fritz London suggested that superfluid helium is a macroscopic liquid matter wave, as a consequence of Bose–Einstein condensation a view opposed Landau. The theoretical work of Bogoliubov, Onsager, Penrose, Feynman (1940s–1950s) elucidated the relation between superfluidity and Bose-condensation. In 1995 Bose–Einstein condensation was experimentally realized in an atomic Bose-gas by the research groups of Cornell and Wieman at JILA, of Ketterle at MIT, and of Hulet at Rice University. In 1999 superfluidity was demonstrated through vorticity in a dilute Bose Gas (Cornell, Wieman, Dalibard, Ketterle et al.). In 2003–2005 Bose–Einstein condensation of pairs, and subsequently superfluidity as again characterized through vortices, was realized in Fermi gases (Zwierlein, Ketterle, Jin). The relation between superfluidity and Bose-condensation was confirmed and clarified by these investigations on ultracold atomic gases, as these systems offer an unprecedented level of control on the interaction strength, dimensionality, density and temperature. As a quantum simulator, systems of ultracold atoms continue to provide insight into different phases of nuclear, atomic, molecular, and condensed matter.