Quantum interference between vortex- and impurity-bound states boosts thermoelectricity

Abstract

Thermoelectric effects in superconductors are generally suppressed by the approximate particle-hole symmetry of the quasiparticle spectrum, but can become pronounced near defects that host particle-hole asymmetric bound states. Here, we investigate how the local thermoelectric response is modified when multiple vortices or nonmagnetic impurities are brought into proximity. Using a lattice Bogolioubov-de Gennes approach combined with linear-response tunneling theory, we calculate the spatially resolved density of states and Seebeck coefficient in $s$- and $d$-wave superconductors. We find that the thermoelectric response can be strongly enhanced when spatially extended defect-induced states overlap. For vortices, this enhancement persists beyond the immediate core regions and originates from interference between vortex-bound states. For impurities, the thermoelectric response exhibits a comparable dependence on impurity separation in the $s$- and $d$-wave cases, although the associated spectral reconstruction is considerably more localized in the $s$-wave superconductor. Our results show that the spatial extent and interference of defect-induced quasiparticle states provide a means of controlling local thermoelectricity in inhomogeneous superconductors, with potential relevance for cryogenic thermoelectric sensing and energy conversion.