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arXiv 1605.04641cond-mat.str-el
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吸引哈伯德模型中BCS到BEC交叉的有效哈密顿蒙特卡罗方法

Effective Hamiltonian based Monte Carlo for the BCS to BEC crossover in the attractive Hubbard model

Kanika Pasrija, Prabuddha B. Chakraborty, Sanjeev Kumar

摘要:

提出了一种有效的基于哈密顿量的实空间方法,研究了有限温度下二维吸引哈伯德模型中弱耦合的Bardeen-Cooper-Schrieffer(BCS)到强耦合的BEC玻色-爱因斯坦凝聚体(BEC)的交叉.我们引入并证明了一个有效的经典哈密顿量来描述相关辅助场的热涨落。我们的结果$T_c$和相图比较非常好,从更复杂的和{ \it CPU}密集的数值方法。我们表明,该方法的工作在无序的存在下,是有用的一个真正的空间描述的无序对超导性的影响。通过对超导序参量、辅助场分布和准粒子态密度的综合分析,我们确定了金属态、绝缘态、超导态和赝能隙态的区域。我们发现的相位起伏的赝能隙行为的重要性是一致的,从最近的实验中得出的结论NbN超导体。通过确定相关的辅助变量,该方法可以推广到研究具有非平凡序参量对称性的超导体。

英文摘要:

We present an effective Hamiltonian based real-space approach for studying the weak-coupling Bardeen-Cooper-Schrieffer (BCS) to the strong-coupling Bose-Einstein condensate (BEC) crossover in the two-dimensional attractive Hubbard model at finite temperatures. We introduce and justify an effective classical Hamiltonian to describe the thermal fluctuations of the relevant auxiliary fields. Our results for $T_c$ and phase diagrams compare very well with those obtained from more sophisticated and {\it cpu}-intensive numerical methods. We demonstrate that the method works in the presence of disorder and is useful for a real-space description of the effect of disorder on superconductivity. From a combined analysis of the superconducting order parameter, the distribution of auxiliary fields and the quasiparticle density of states, we identify the regions of metallic, insulating, superconducting and pseudogapped behavior. Our finding of the importance of phase fluctuations for the pseudogap behavior is consistent with the conclusions drawn from recent experiments on NbN superconductors. The method can be generalized to study superconductors with non-trivial order parameter symmetries by identifying the relevant auxiliary variables.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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