Cooper pairing and BCS-BEC evolution in mixed-dimensional Fermi gases
Cooper pairing and BCS-BEC evolution in mixed-dimensional Fermi gases
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DOI：
10.1103/physreva.82.063628
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发表时间：
2010-12-27
影响因子：
2.9
通讯作者：
Subasi, A. L.
中科院分区：
文献类型：
--
作者：
Iskin, M.;Subasi, A. L.
类似于最近在玻色-玻色混合物中取得的成就[G。Lamporesi， J. Catani， G. Barontini， Y. Nishida， M. Inguscio和F. Minardi，物理学家。[Rev. Lett. 104, 153202(2010)]，混合维费米-费米混合物可以通过在两种费米气体（sigma相当于{向上箭头，向下箭头}）上应用种选择的一维光学晶格来创建，这样两个种都被限制在由它们沿着晶格方向跳跃决定的准二维几何形状中。我们研究了BCS-BEC演化过程中这类混合物的基态超流体相图，发现了正常、间隙超流体、无间隙超流体和相分离区域。特别是，我们发现了一个稳定的无间隙超流体相，其中未配对的向上箭头和向下箭头费米子与不同动量空间区域的成对（或超流体）费米子共存。这个相在某些方面类似于在密度混合物中发现的Sarma状态，但在我们的情况下，无间隙超流体相是非极化的，最重要的是它在相分离时是稳定的。
Similar to what has recently been achieved with Bose-Bose mixtures [G. Lamporesi, J. Catani, G. Barontini, Y. Nishida, M. Inguscio, and F. Minardi, Phys. Rev. Lett. 104, 153202 (2010)], mixed-dimensional Fermi-Fermi mixtures can be created by applying a species-selective one-dimensional optical lattice to a two-species Fermi gas (sigma equivalent to {up arrow,down arrow}), in such a way that both species are confined to quasi-two-dimensional geometries determined by their hoppings along the lattice direction. We investigated the ground-state phase diagram of superfluidity for such mixtures in the BCS-BEC evolution, and found normal, gapped superfluid, gapless superfluid, and phase separated regions. In particular, we found a stable gapless superfluid phase where the unpaired up arrow and down arrow fermions coexist with the paired (or superfluid) ones in different momentum space regions. This phase is in some ways similar to the Sarma state found in mixtures with densities, but in our case, the gapless superfluid phase is unpolarized and most importantly it is stable against phase separation.