Impurity effects on BCS-BEC crossover in ultracold atomic Fermi gases
Impurity effects on BCS-BEC crossover in ultracold atomic Fermi gases
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DOI：
10.1103/physrevb.95.014504
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发表时间：
2016-08
影响因子：
3.7
通讯作者：
Yanming Che;Qijin Chen
中科院分区：
文献类型：
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作者：
Yanming Che;Qijin Chen
本文用对涨落理论系统地研究了费米原子气体中杂质对s$波BCS-BEC渡越的影响。配对和杂质散射$T$-矩阵处理自洽在同一时间。在玻恩极限下，系统对杂质散射不太敏感，但对于强杂质散射，频率和差距函数都被高度重整化，导致超流T_c$、序参量和超流密度的显著抑制。我们还发现了费米子态密度中杂质带的形成和相干峰的拖尾，导致了Bogoliubov准粒子的谱权转移和有限寿命。在BCS区，高密度杂质很容易破坏超流性。相比之下，在幺正和BEC制度的超流性是相对更强大的。
We present a systematic investigation of the effects of "nonmagnetic" impurities on the $s$-wave BCS-BEC crossover in atomic Fermi gases within a pairing fluctuation theory. Both pairing and impurity scattering $T$-matrices are treated self-consistently at the same time. While the system is less sensitive to impurity scattering in the Born limit, for strong impurity scatterers, both the frequency and the gap function are highly renormalized, leading to significant suppression of the superfluid $T_c$, the order parameter and the superfluid density. We also find the formation of impurity bands and smearing of coherence peak in the fermion density of states, leading to a spectrum weight transfer and finite lifetime of Bogoliubov quasiparticles. In the BCS regime, the superfluidity may be readily destroyed by the impurity of high density. In comparison, the superfluidity in unitary and BEC regimes is relatively more robust.