平带超导体中的Escherasekhar-Clogston极限
Going beyond the Chandrasekhar-Clogston limit in a flat-band superconductor
摘要：
通常情况下，自旋单重态超导的磁场强度会受到严格的限制，导致临界感应塞曼位移仅为超导能隙的一小部分。在这里，我们考虑一个模型系统中的自旋单态库珀配对的色散带交叉费米能级是由一个额外的平带远离费米能级。在色散带中的配对的提升允许非平凡的解决方案的耦合间隙方程的自旋分裂场大大大于超导间隙在零场。此外，平带中远离费米能级的附加库珀配对增加了超导凝聚能，而不影响系统的顺磁磁化率，使自由能有利于超导态。这为自旋单态超导性超出标准的克拉塞卡-克罗格斯顿极限开辟了可能性。
英文摘要：
The Chandrasekhar-Clogston limit normally places stringent conditions on the magnitude of the magnetic field that can coexist with spin-singlet superconductivity, restricting the critical induced Zeeman shift to a fraction of the superconducting gap. Here, we consider a model system where the spin-singlet Cooper pairing in a dispersive band crossing the Fermi level is boosted by an additional flat-band located away from the Fermi level. The boosting of the pairing in the dispersive band allows for nontrivial solutions to the coupled gap equations for spin-splitting fields considerably larger than the superconducting gaps at zero field. Further, the additional Cooper pairing in the flat-band, away from the Fermi level, increases the superconducting condensation energy without affecting the paramagnetic susceptibility of the system, making the free energy favor the superconducting state. This opens up the possibility for spin-singlet superconductivity beyond the standard Chandrasekhar-Clogston limit.
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