Spin-imbalance in a one-dimensional Fermi gas

Superconductivity and magnetism generally do not coexist. Changing the relative number of up and down spin electrons disrupts the basic mechanism of superconductivity, where atoms of opposite momentum and spin form Cooper pairs. Nearly forty years ago Fulde and Ferrell and Larkin and Ovchinnikov (FF...

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Bibliographic Details
Published in:Nature (London) 2010-09, Vol.467 (7315), p.567-569
Main Authors: Hulet, Randall G, Liao, Yean-an, Rittner, Ann Sophie C, Paprotta, Tobias, Li, Wenhui, Partridge, Guthrie B, Baur, Stefan K, Mueller, Erich J
Format: Article
Language:English
Subjects:
639/766/25
Atoms & subatomic particles
Classical and quantum physics: mechanics and fields
Exact sciences and technology
Experiments
Fermions
Gases
Humanities and Social Sciences
letter
Magnetism
Matter waves
multidisciplinary
Particle spin
Physics
Properties
Science
Science (multidisciplinary)
Superconductivity
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Summary:Superconductivity and magnetism generally do not coexist. Changing the relative number of up and down spin electrons disrupts the basic mechanism of superconductivity, where atoms of opposite momentum and spin form Cooper pairs. Nearly forty years ago Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) proposed an exotic pairing mechanism in which magnetism is accommodated by the formation of pairs with finite momentum. Despite intense theoretical and experimental efforts, however, polarized superconductivity remains largely elusive. Unlike the three-dimensional (3D) case, theories predict that in one dimension (1D) a state with FFLO correlations occupies a major part of the phase diagram. Here we report experimental measurements of density profiles of a two-spin mixture of ultracold 6Li atoms trapped in an array of 1D tubes (a system analogous to electrons in 1D wires). At finite spin imbalance, the system phase separates with an inverted phase profile, as compared to the 3D case. In 1D, we find a partially polarized core surrounded by wings which, depending on the degree of polarization, are composed of either a completely paired or a fully polarized Fermi gas. Our work paves the way to direct observation and characterization of FFLO pairing.
ISSN:0028-0836
1476-4687
DOI:10.1038/nature09393