Shockley-Ramo theorem and long-range photocurrent response in gapless materials

TL;DR

This paper introduces a Shockley-Ramo-based framework to explain complex photocurrent patterns in gapless materials like graphene, revealing how these patterns can inform about local material properties.

Contribution

The authors develop a general theoretical approach to interpret long-range photocurrent responses in gapless materials, connecting observed patterns to material symmetry and inhomogeneity.

Findings

Photocurrent patterns can be explained by a Shockley-Ramo-type approach.

Patterns reveal information about symmetry breaking and local inhomogeneities.

The framework applies to various gapless materials like graphene.

Abstract

Scanning photocurrent maps of gapless materials, such as graphene, often exhibit complex patterns of hot spots positioned far from current-collecting contacts. We develop a general framework that helps to explain the unusual features of the observed patterns, such as the directional effect and the global character of photoresponse. We show that such a response is captured by a simple Shockley-Ramo-type approach. We examine specific examples and show that the photoresponse patterns can serve as a powerful tool to extract information about symmetry breaking, inhomogeneity, chirality, and other local characteristics of the system.