Strongly enhanced tunneling at total charge neutrality in double bilayer graphene-WSe$_2$ heterostructures

TL;DR

This paper reports the experimental discovery of strongly enhanced tunneling in double bilayer graphene heterostructures at total charge neutrality, indicating possible many-body excitonic states.

Contribution

It provides the first experimental evidence of enhanced tunneling at neutrality in graphene heterostructures, suggesting the formation of interbilayer excitons beyond single-particle models.

Findings

Enhanced tunneling increases sharply as temperature decreases.

Tunneling current shows a vertical onset at low temperature.

Deviation from single-particle models indicates many-body effects.

Abstract

We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe$_2$ barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.