Vertex corrections to nonlinear photoinduced currents in two-dimensional superconductors

A. V. Parafilo; V. M. Kovalev; I. G. Savenko

doi:10.1103/9prb-whh8

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Vertex corrections to nonlinear photoinduced currents in two-dimensional superconductors

A. V. Parafilo, V. M. Kovalev, I. G. Savenko

DOI 10.1103/9prb-whh8 · Physical Review B

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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.