Nonlinear, anisotropic and giant photoconductivity in intrinsic and doped graphene

TL;DR

This paper develops a comprehensive framework to calculate nonlinear and anisotropic photoconductivity in graphene, revealing giant, polarization-dependent responses that can be experimentally distinguished from thermal effects.

Contribution

It introduces a non-perturbative method to compute all-order photoconductivity in graphene, highlighting giant, anisotropic responses linked to incident light polarization.

Findings

Photoconductivity in graphene is giant at high optical fields.

The response is highly anisotropic and polarization-dependent.

Distinct experimental signatures can differentiate photovoltaic effects from thermal effects.

Abstract

We present a framework to calculate the anisotropic and non-linear photoconductivity for two band systems with application to graphene. In contrast to the usual perturbative (second order in the optical field strength) techniques, we calculate photoconductivity to all orders in the optical field strength. In particular, for graphene, we find the photoresponse to be giant (at large optical field strengths) and anisotropic. The anisotropic photoresponse in graphene is correlated with polarization of the incident field, with the response being similar to that of a half-wave plate. We predict that the anisotropy in the simultaneous measurement of longitudinal ($\sigma_{xx}$) and transverse $(\sigma_{yx})$ photoconductivity, with four probes, offers a unique experimental signature of the photo-voltaic response, distinguishing it from the thermal-Seebeck and bolometric effects in photoresponse.