Controlling the pair momentum of the Fulde-Ferrell-Larkin-Ovchinnikov state in a three-dimensional Fermi gas through a one-dimensional periodic potential
Controlling the pair momentum of the Fulde-Ferrell-Larkin-Ovchinnikov state in a three-dimensional Fermi gas through a one-dimensional periodic potential
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DOI：
10.1103/physreva.84.043623
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发表时间：
2011-07
影响因子：
2.9
通讯作者：
Jeroen P. A. Devreese;M. Wouters;J. Tempere
中科院分区：
文献类型：
--
作者：
Jeroen P. A. Devreese;M. Wouters;J. Tempere
自旋不平衡的费米气体是否能容纳富尔德-费雷尔-拉金-奥夫钦尼科夫（FFLO）态的问题一直是深入研究的主题。在这种状态下，库珀对获得非零动量，迄今为止还没有实验观察到。最近，我们证明了FFLO状态可以稳定在一个三维费米气体，通过添加一个一维周期性的潜力。到目前为止，假设FFLO波矢量总是平行于该周期势（FFLO-P）。在这篇文章中，我们发现，令人惊讶的是，FFLO波矢量也可以相对于势（FFLO-S）倾斜。从配分和出发，在路径积分形式下导出了系统的鞍点自由能。最小化这种自由能使我们能够研究系统的不同竞争基态。为了定性地理解潜在的配对机制，我们可视化自旋向上和自旋向下的粒子的费米表面。从这个可视化，我们发现，倾斜的FFLO波矢量相对于周期性电位的方向可以导致在两个自旋物种的配对带之间的更大的重叠。这种偏斜的FFLO态可以为观察3D费米气体中的FFLO超流性提供额外的实验特征。
The question whether a spin-imbalanced Fermi gas can accommodate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state has been the subject of intense study. This state, in which Cooper pairs obtain a nonzero momentum, has hitherto eluded experimental observation. Recently, we demonstrated that the FFLO state can be stabilized in a 3D Fermi gas, by adding a 1D periodic potential. Until now it was assumed that the FFLO wave vector always lies parallel to this periodic potential (FFLO-P). In this contribution we show that, surprisingly, the FFLO wave vector can also lie skewed with respect to the potential (FFLO-S). Starting from the partition sum, the saddle-point free energy of the system is derived within the path-integral formalism. Minimizing this free energy allows us to study the different competing ground states of the system. To qualitatively understand the underlying pairing mechanism, we visualize the Fermi surfaces of the spin-up and spin-down particles. From this visualization, we find that tilting the FFLO wave vector with respect to the direction of the periodic potential can result in a larger overlap between the pairing bands of both spin species. This skewed FFLO state can provide an additional experimental signature for observing FFLO superfluidity in a 3D Fermi gas.