Superfluid density of a spin-orbit-coupled Bose gas

Year: 2016

Authors: Zhang YC., Yu ZQ., Ng TK., Zhang SZ., Pitaevskii L., Stringari S.

Autors Affiliation: Univ Hong Kong, Dept Phys, Hong Kong, Hong Kong, Peoples R China; Univ Hong Kong, Ctr Theoret & Computat Phys, Hong Kong, Hong Kong, Peoples R China; Shanxi Univ, Inst Theoret Phys, Taiyuan 030006, Peoples R China; Hong Kong Univ Sci & Technol, Dept Phys, Kowloon, Hong Kong, Peoples R China; Univ Trento, INO CNR BEC Ctr, Via Sommarive 14, Povo, Italy; Univ Trento, Dept Phys, Via Sommarive 14, Povo, Italy; RAS, Kapitza Inst Phys Problems, Kosygina 2, Moscow 119334, Russia.

Abstract: We discuss the superfluid properties of a uniform, weakly interacting Bose-Einstein condensed gas with spin-orbit coupling, realized recently in experiments. We find a finite normal fluid density rho(n) at zero temperature which turns out to be a function of the Raman coupling. In particular, the entire fluid becomes normal at the transition point from the zero momentum to the plane wave phase, even though the condensate fraction remains finite. We emphasize the crucial role played by the breaking of Galilean invariance and by the gapped branch of the elementary excitations whose contribution to various sum rules is discussed explicitly. Our predictions for the superfluid density are successfully compared with the available experimental results based on the measurement of the sound velocities.

Journal/Review: PHYSICAL REVIEW A

Volume: 94 (3)      Pages from: 33635-1  to: 33635-5

More Information: We would like to thank Anthony Leggett for discussions. Y.C. and S.Z. are supported by the Hong Kong Research Grants Council, General Research Fund, HKU 17306414 and the Croucher Foundation under the Croucher Innovation Award. T.K. and S.Z. are supported by the CRF, HKUST3/CRF/13G. Z.Q.Y. is supported by NSFC under Grant No. 11674202. L.P and S.S. are supported by ERC through a QGBE grant, by a QUIC grant of the Horizon2020 FET program, and by Provincia Autonoma di Trento.
KeyWords: Liquid
DOI: 10.1103/PhysRevA.94.033635

Citations: 44
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