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.
@article{arxiv.1112.5654,
title = {Shockley-Ramo theorem and long-range photocurrent response in gapless materials},
author = {Justin C. W. Song and Leonid S. Levitov},
journal= {arXiv preprint arXiv:1112.5654},
year = {2015}
}