Vertex corrections to nonlinear photoinduced currents in two-dimensional superconductors
Phys. Rev. B 112, 134513 – Published 14 October, 2025
DOI: https://doi.org/10.1103/9prb-whh8
Abstract
The emergence of a rectified steady-state supercurrent as a response to the photoexcited current of the quasiparticles constitutes the concept of a superconducting photodiode. This phenomenon occurs in a two-dimensional thin, superconducting film with a built-in DC supercurrent, which is exposed to the circularly polarized external electromagnetic field. The flow of a Cooper-pair condensate, resulting as a second-order photoresponse in a direction transverse to the initially built-in supercurrent, represents a superconducting counterpart to the photogalvanic effect. In this paper, we examine the photodiode supercurrent by restoring gauge invariance within the mean-field BCS framework. To achieve this, we derive an impurity-sensitive BCS-interaction-induced correction to the vertex function by performing self-consistent calculations within the Keldysh Green's function technique. The resulting photodiode current can be utilized for spectroscopic analysis of typical relaxation times in superconducting films.
