在有吸引力的哈伯德模型中通过分层增加超导 $T_c$

Rodrigo A. Fontenele, Natanael C. Costa, Thereza Paiva, Raimundo R. dos Santos
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引用次数: 0

摘要

有吸引力的哈伯德模型已经成为一种很容易在光学晶格上用超冷原子实现的模型。然而,超导(超流体)临界温度($T_c$'s)仍略低于实验中达到的最低温度。我们进行了无负号行列式量子蒙特卡洛模拟,以计算配对相关函数、均匀自旋感度和双占位等响应函数,并通过这些函数绘制出一些物理特性。我们发现,通过对填充物和现场吸引力强度的明智选择,双层的 $T_c$ 值可以是单层的 1.5 到 1.7 倍;对于简单立方晶格,这种增强可以比单层的最大值大 30%。我们还检验了有吸引力哈巴模型中类似于 BCS 的 $T_c$ 估计值以及基于超密度的 $T_c$ 上限的准确性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Increasing superconducting $T_c$ by layering in the attractive Hubbard model
The attractive Hubbard model has become a model readily realizable with ultracold atoms on optical lattices. However, the superconducting (superfluid) critical temperatures, $T_c$'s, are still somewhat smaller than the lowest temperatures achieved in experiments. Here we consider two possible routes, generically called layering, to increase $T_c$: a bilayer and a simple cubic lattice, both with tunable hopping, $t_z$, between attractive Hubbard planes. We have performed minus-sign--free determinant quantum Monte Carlo simulations to calculate response functions such as pairing correlation functions, uniform spin susceptibility, and double occupancy, through which we map out some physical properties. We have found that by a judicious choice of fillings and intensity of on-site attraction, a bilayer can exhibit $T_c$'s between 1.5 and 1.7 times those of the single layer; for the simple-cubic lattice the enhancement can be 30\% larger than the maximum for the single layer. We also check the accuracy of both a BCS-like estimate for $T_c$ in the attractive Hubbard model, as well as of an upper bound for $T_c$ based on the superfluid density.
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