Density and spin linear response of atomic Fermi superfluids with population imbalance in the BCS-BEC crossover

被引:5
作者
Guo, Hao [1 ]
Li, Yang [1 ]
He, Yan [2 ,3 ]
Chien, Chih-Chun [4 ,5 ]
机构
[1] Southeast Univ, Dept Phys, Nanjing 211189, Jiangsu, Peoples R China
[2] Univ Chicago, James Franck Inst, Chicago, IL 60637 USA
[3] Univ Chicago, Dept Phys, Chicago, IL 60637 USA
[4] Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA
[5] Univ Calif, Sch Nat Sci, Merced, CA 95343 USA
基金
中国国家自然科学基金;
关键词
superfluid; linear response theory; Fermi gas; gauge invariance; SUPERCONDUCTIVITY; GAS; CONDENSATION; TRANSITION;
D O I
10.1088/0953-4075/47/8/085302
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
We present a theoretical study of the density and spin (representing the two components) linear response of Fermi superfluids with tunable attractive interactions and population imbalance. In both linear response theories, we find that the fluctuations of the order parameter must be treated on equal footing with the gauge transformations associated with the symmetries of the Hamiltonian so that important constraints including various sum rules can be satisfied. Both theories can be applied to the whole BCS-Bose-Einstein condensation crossover. The spin linear responses are qualitatively different with and without population imbalance because collective-mode effects from the fluctuations of the order parameter survive in the presence of population imbalance, even though the associated symmetry is not broken by the order parameter. Since a polarized superfluid becomes unstable at low temperatures in the weak and intermediate coupling regimes, we found that the density and spin susceptibilities diverge as the system approaches the unstable regime, but the emergence of phase separation preempts the divergence.
引用
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页数:15
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