Visualizing electrostatic gating effects in two-dimensional heterostructures

TL;DR

This paper demonstrates how micro-ARPES can directly visualize and measure electronic band structure changes in 2D heterostructures under electrostatic gating, revealing shifts in chemical potential, band edges, and band-gap renormalization.

Contribution

It introduces the application of micro-ARPES to study electrostatic gating effects in 2D heterostructures, enabling direct observation of electronic structure modifications.

Findings

Chemical potential shifts by 0.6 eV in graphene under gating

Conduction band edge observed in 2D semiconductors with electron accumulation

Significant band-gap renormalization at low electron densities

Abstract

The ability to directly observe electronic band structure in modern nanoscale field-effect devices could transform understanding of their physics and function. One could, for example, visualize local changes in the electrical and chemical potentials as a gate voltage is applied. One could also study intriguing physical phenomena such as electrically induced topological transitions and many-body spectral reconstructions. Here we show that submicron angle-resolved photoemission (micro-ARPES) applied to two-dimensional (2D) van der Waals heterostructures affords this ability. In graphene devices, we observe a shift of the chemical potential by 0.6 eV across the Dirac point as a gate voltage is applied. In several 2D semiconductors we see the conduction band edge appear as electrons accumulate, establishing its energy and momentum, and observe significant band-gap renormalization at low densities. We also show that micro-ARPES and optical spectroscopy can be applied to a single device, allowing rigorous study of the relationship between gate-controlled electronic and excitonic properties.