Breaking the superfluid speed limit in a fermionic condensate

Bradley, David Ian and Fisher, Shaun Neil and Guénault, Anthony Michael and Haley, Richard Peter and Lawson, Christopher and Pickett, George Richard and Schanen, Roch and Skyba, Maros and Tsepelin, Viktor and Zmeev, Dmitriy (2016) Breaking the superfluid speed limit in a fermionic condensate. Nature physics, 12 (11). pp. 1017-1021. ISSN 1745-2473

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Abstract

Coherent condensates appear as emergent phenomena in many systems. They share the characteristic feature of an energy gap separating the lowest excitations from the condensate ground state. This implies that a scattering object, moving through the system with high enough velocity for the excitation spectrum in the scatterer frame to become gapless, can create excitations at no energy cost, initiating the breakdown of the condensate—the well-known Landau velocity. Whereas, for the neutral fermionic superfluid 3He-B in the T = 0 limit, flow around an oscillating body displays a very clear critical velocity for the onset of dissipation, here we show that for uniform linear motion there is no discontinuity whatsoever in the dissipation as the Landau critical velocity is passed and exceeded. Given the importance of the Landau velocity for our understanding of superfluidity, this result is unexpected, with implications for dissipative effects of moving objects in all coherent condensate systems.

Item Type: Journal Article
Journal or Publication Title: Nature physics
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/3100
Subjects:
Departments: Faculty of Science and Technology > Physics
ID Code: 80641
Deposited By: ep_importer_pure
Deposited On: 15 Sep 2016 13:36
Refereed?: Yes
Published?: Published
Last Modified: 14 Oct 2019 08:30
URI: https://eprints.lancs.ac.uk/id/eprint/80641

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