Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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 proposed an
exotic pairing mechanism (FFLO) where magnetism is accommodated by formation of
pairs with finite momentum. Despite intense theoretical and experimental
efforts, however, polarized superconductivity remains largely elusive. Here we
report experimental measurements of density profiles of a two spin mixture of
ultracold 6Li atoms trapped in an array of one dimensional (1D) tubes, a system
analogous to electrons in 1D wires. At finite spin imbalance, the system phase
separates with an inverted phase profile in comparison to the three-dimensional
case. In 1D we find a partially polarized core surrounded by wings composed of
either a completely paired BCS superfluid or a fully polarized Fermi gas,
depending on the degree of polarization. Our observations are in quantitative
agreement with theoretical calculations in which the partially polarized phase
is found to be a 1D analogue of the FFLO state. This study demonstrates how
ultracold atomic gases in 1D may be used to create non-trivial new phases of
matter, and also paves the way for direct observation and further study of the
FFLO phase.

29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin