Supercurrent induced resonant optical response

Philip J. D. Crowley; Liang Fu

doi:10.1103/physrevb.106.214526

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arXiv · 2203.06192

Supercurrent induced resonant optical response

Philip J. D. Crowley·Liang Fu

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Abstract

The optical conductivity encodes the current response to a time dependent electric field. We develop a theory of the optical conductivity $\sigma(\omega)$ in presence of a dc supercurrent. Current induced optical response is prohibited by Galilean invariance from occurring in systems with a single parabolic band. However, we show that lattice effects give rise to a pronounced current dependent peak in $\sigma(\omega)$ at the gap edge $\omega = 2 \Delta$, which diverges in the clean limit. We demonstrate this in a model of a multi-band superconductor. Our theory explains the recent observation of a current induced peak in the optical conductivity in NbN by Nakamura et al. (2019), and provides a new mechanism for direct activation of the Higgs mode with light.

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Philip J. D. Crowley, Liang Fu. 2022-03-11. Supercurrent induced resonant optical response. https://doi.org/10.1103/physrevb.106.214526

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