论文标题
Yu-Shiba-Rusinov指出，BCS-BEC交叉和平面极限的精确解决方案
Yu-Shiba-Rusinov states, the BCS-BEC crossover, and the exact solution in the flat-band limit
论文作者
论文摘要
我们研究了理查森（Richardson）的超导体模型中的子级Yu-Shiba-Rusinov（YSR）状态，该模型具有磁性杂质，可从弱耦合Bardeen-cooper-schrieffer（BCS）方案中具有不同的电子配对强度，以实现强耦合Bose-bose-bose-bose-bose-bose-Instein-Instein-Instein-odenstein-odencondensate（becy）。我们观察到，配对强度提高对YSR激发光谱的影响是杂交强度和杂质现场电位的函数的作用，仅是定量的，实际上，当结果适当地重新缩放时，实际上很弱。此外，我们还表明，在深度BEC极限上可以在分析上解决该问题，这相当于平坦的超导性。这种精确的溶液可以与零伴随宽（ZBW）有效的BCS平均磁场hamiltonian有关，其中超导体由单个电子水平与现场配对描述。理查森模型的BCS和BEC政权之间的微小差异解释了简单的ZBW计算对BCS平均野战汉密尔顿人的成功。 ZBW模型仅需要一个合适的参数重新缩放才能作为整个问题的定量预测工具有用。
We study the subgap Yu-Shiba-Rusinov (YSR) states in the Richardson's model of a superconductor with a magnetic impurity for different electron pairing strengths from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime to the strong-coupling Bose-Einstein-condensate (BEC) regime. We observe that the effect of the increasing pairing strength on the YSR excitation spectrum as a function of hybridisation strength and impurity on-site potential is only quantitative and, in fact, rather weak when the results are appropriately rescaled. We furthermore show that the problem is analytically solvable in the deep BEC limit which is equivalent to flat-band superconductivity. This exact solution can be related to a zero-bandwidth (ZBW) effective BCS mean field Hamiltonian where the superconductor is described by a single electron level with onsite pairing. The small difference between the BCS and BEC regimes of the Richardson's model explains the success of the simple ZBW calculations for BCS mean-field Hamiltonians. A ZBW model requires only a suitable parameter rescaling to become useful as a quantitative predictive tool for the full problem.
