Electrical detection of the flat band dispersion in van der Waals field-effect structures

TL;DR

This paper demonstrates an electrical method to detect the flat band dispersion in van der Waals heterostructures, specifically using tunneling photocurrents in InSe, enabling easier investigation of flat-band physics at room temperature.

Contribution

It introduces a novel electrical detection technique for flat band positions in 2D materials using tunneling currents, without needing twist angles or complex setups.

Findings

Tunneling photocurrents reveal the flat band in InSe.

Presence of van Hove singularity causes a sharp change in tunneling behavior.

Method is effective at room temperature.

Abstract

Two-dimensional flat-band systems have recently attracted considerable interest due to the rich physics unveiled by emergent phenomena and correlated electronic states at van Hove singularities. However, the difficulties in electrically detecting the flat band position in field-effect structures are slowing down the investigation of their properties. In this work, we employ Indium Selenide (InSe) as a flat-band system due to a van Hove singularity at the valence band edge in a few-layer form of the material without the requirement of a twist angle. We investigate tunneling photocurrents in gated few-layer InSe structures and relate them to ambipolar transport and photoluminescence measurements. We observe an appearance of a sharp change in tunneling mechanisms due to the presence of the van Hove singularity at the flat band. We further corroborate our findings by studying tunneling currents as a reliable probe for the flat-band position up to room temperature. Our results create an alternative approach to studying flat-band systems in heterostructures of 2D materials.