Modeling of Plasmonic and Polaritonic Effects in Photocurrent Nanoscopy

TL;DR

This paper develops a modeling framework for understanding collective mode effects in photocurrent measurements of 2D materials, accounting for various contributions and spatial oscillations observed in nanoscale optical experiments.

Contribution

It introduces a comprehensive model that captures photothermal, photovoltaic, and bolometric effects, explaining spatial oscillations and linking photocurrent nanoscopy to near-field optical microscopy.

Findings

Model accounts for periodic photocurrent fringes near edges and inhomogeneities.

Identifies dominant photocurrent mechanisms based on experimental conditions.

Establishes a relation between photocurrent spectra and near-field optical measurements.

Abstract

We present a basic framework for modeling collective mode effects in photocurrent measurements performed on two-dimensional materials using nano-optical scanned probes. We consider photothermal, photovoltaic, and bolometric contributions to the photocurrent. We show that any one of these can dominate depending on frequency, temperature, applied bias, and sample geometry. Our model is able to account for periodic spatial oscillations (fringes) of the photocurrent observed near sample edges or inhomogeneities. For the case of a non-absorbing substrate, we find a direct relation between the spectra measured by the photocurrent nanoscopy and its parental scanning technique, near-field optical microscopy.