Confined Trions and Mott-Wigner States in a Purely Electrostatic Moir\'e Potential

TL;DR

This study demonstrates how a purely electrostatic moiré potential generated by ferroelectric domains in h-BN can induce correlated electronic states, including Mott-Wigner states, in a TMD monolayer, evidenced by excitonic and trionic signatures.

Contribution

It introduces a novel electrostatic approach to create moiré potentials in TMDs using ferroelectric domain structures, revealing new correlated electronic states.

Findings

Observation of new excitonic resonances at integer fillings.

Enhancement of trion binding energy by approximately 3 meV.

Evidence of charge order linked to Mott-Wigner states at specific fillings.

Abstract

Moir\'e heterostructures consisting of transition metal dichalcogenide (TMD) hetero- and homobilayers have emerged as a promising material platform to study correlated electronic states. Optical signatures of strong correlations in the form of Mott-Wigner states and fractional Chern insulators have already been observed in TMD monolayers and their twisted bilayers. In this work, we use a moir\'e substrate containing a twisted hexagonal boron nitride (h-BN) interface to externally generate a superlattice potential for the TMD layer: the periodic structure of ferroelectric domains in h-BN effects a purely electrostatic potential for charge carriers. We find direct evidence for the induced moir\'e potential in the emergence of new excitonic resonances at integer fillings, and our observation of an enhancement of the trion binding energy by $\simeq$ 3 meV. A theoretical model for exciton-electron interactions allows us to directly determine the moir\'e potential modulation of 30$\pm$5 meV from the measured trion binding energy shift. We obtain direct evidence for charge order linked to electronic Mott-Wigner states at filling factors $\nu$ = 1/3 and $\nu$ = 2/3 through the associated exciton Umklapp resonances.