He Yuan-Yao, Shi Hao, Zhang Shiwei
Institute of Modern Physics, Northwest University, Xi'an 710127, China.
Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi'an 710127, China.
Phys Rev Lett. 2022 Aug 12;129(7):076403. doi: 10.1103/PhysRevLett.129.076403.
We perform large-scale, numerically exact calculations on the two-dimensional interacting Fermi gas with a contact attraction. Reaching much larger lattice sizes and lower temperatures than previously possible, we determine systematically the finite-temperature phase diagram of the Berezinskii-Kosterlitz-Thouless (BKT) transitions for interaction strengths ranging from BCS to crossover to BEC regimes. The evolutions of the pairing wave functions and the fermion and Cooper pair momentum distributions with temperature are accurately characterized. In the crossover regime, we find that the contact has a nonmonotonic temperature dependence, first increasing as temperature is lowered, and then showing a slight decline below the BKT transition temperature to approach the ground-state value from above.
我们对具有接触吸引作用的二维相互作用费米气体进行了大规模的数值精确计算。我们达到了比以往更大的晶格尺寸和更低的温度，系统地确定了从BCS到交叉再到BEC区域的相互作用强度下，Berezinskii-Kosterlitz-Thouless（BKT）转变的有限温度相图。精确地表征了配对波函数以及费米子和库珀对动量分布随温度的演化。在交叉区域，我们发现接触具有非单调的温度依赖性，首先随着温度降低而增加，然后在低于BKT转变温度时略有下降，从上方趋近基态值。
