Geometric photon-drag effect and nonlinear shift current in centrosymmetric crystals

TL;DR

This paper reveals that a photon-drag effect can induce a nonlinear shift current in centrosymmetric crystals, which was previously thought impossible, offering new ways to probe material properties.

Contribution

It demonstrates that photon-drag can activate a shift current in centrosymmetric crystals, highlighting a geometric origin and transverse response of this effect.

Findings

Photon-drag shift current is transverse and geometric in origin.

This effect can be enhanced by polariton coupling.

It enables probing interband coherences in inversion-symmetric materials.

Abstract

The nonlinear shift current, also known as the bulk photovoltaic current generated by linearly polarized light, has long been known to be absent in crystals with inversion symmetry. Here we argue that a non-zero shift current in centrosymmetric crystals can be activated by a photon-drag effect. Photon-drag shift current proceeds from a `shift current dipole' (a geometric quantity characterizing interband transitions) and manifests a purely transverse response in centrosymmetric crystals. This transverse nature proceeds directly from the shift-vector's pseudovector nature under mirror operation and underscores its intrinsic geometric origin. Photon-drag shift current can greatly enhanced by coupling to polaritons and provides a new and sensitive tool to interrogate the subtle interband coherences of materials with inversion symmetry previously thought to be inaccessible via photocurrent probes.