Atomic Scale Elastic Textures Coupled to Electrons in Superconductors

Abstract

We present an atomic scale theory of lattice distortions using strain-related variables and their constraint equations. Our approach connects constrained atomic length scale variations to continuum elasticity and can describe elasticity at all length scales. We apply the general approach to a two-dimensional square lattice with a monatomic basis, and find the atomic scale elastic textures around a structural domain wall and a single defect, as exemplar textures. We clarify the microscopic origin of anisotropic gradient terms, some of which are included phenomenologically in Landau–Ginzburg theory. The obtained elastic textures are used to investigate the effects of elasticity-driven lattice deformation on the nanoscale electronic structure in superconductor by solving the Bogliubov–de Gennes equations with the electronic degrees of freedom coupled to the lattice ones. It is shown that the order parameter is depressed in the regions where the lattice deformation takes place. The calculated local density of states suggests the electronic structure is strongly modulated as a response to the lattice deformation—the elasticity propagates the electronic response over long distances. In particular, the trapping of low-lying quasiparticle states around the defects is possible. These predictions could be directly tested by STM experiments in superconducting materials.