论文标题
浆果曲率在二维材料中BCS型超导性中的作用
Role of the Berry curvature on BCS-type superconductivity in two-dimensional materials
论文作者
论文摘要
从理论上讲,当电子可以用有效的单波段哈密顿量描述电子时,在多波段结构中产生的浆果曲率如何影响二维电子系统的超导性能。通常,浆果曲率与周期晶体电位产生的电场耦合到电场。这种电场的潜在来源在晶格尺度上缓慢变化,是电子之间的相互作用。我们表明,浆果曲率在哈密顿式中提供了其他术语,描述了单个频段中的相互作用电子。当在通常的BCS弱耦合处理的框架内考虑到通用有吸引力的相互作用的框架,该术语允许形成库珀对时,耦合常数将被修改。在纯单线和三胞胎超导体中,我们发现浆果曲率通常会降低耦合常数,从而降低了超导间隙和临界温度作为掺杂的函数。从实验的角度来看,掺杂时的预期BCS临界温度的测量偏差,例如在掺杂的二维过渡金属二核化合物中,可以揭示浆果曲率的强度。
We theoretically investigate how the Berry curvature, which arises in multi-band structures when the electrons can be described by an effective single-band Hamiltonian, affects the superconducting properties of two-dimensional electronic systems. Generically the Berry curvature is coupled to electric fields beyond those created by the periodic crystal potential. A potential source of such electric fields, which vary slowly on the lattice scale, is the mutual interaction between the electrons. We show that the Berry curvature provides additional terms in the Hamiltonian describing interacting electrons within a single band. When these terms are taken into account in the framework of the usual BCS weak-coupling treatment of a generic attractive interaction that allows for the formation of Cooper pairs, the coupling constant is modified. In pure singlet and triplet superconductors, we find that the Berry curvature generally lowers the coupling constant and thus the superconducting gap and the critical temperature as a function of doping. From an experimental point of view, a measured deviation from the expected BCS critical temperature upon doping, e.g. in doped two-dimensional transition-metal dichalcogenides, may unveil the strength of the Berry curvature.