Confined Trions and Mott-Wigner States in a Purely Electrostatic Moiré Potential

Moiré heterostructures consisting of transition metal dichalcogenide (TMD) heterobilayers 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 moiré substrate containing a twisted hexagonal boron nitride (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>h</a:mi></a:mrow></a:math>-BN) interface to externally generate a superlattice potential for the TMD layer: The periodic structure of ferroelectric domains in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi>h</c:mi></c:mrow></c:math>-BN creates a purely electrostatic potential for charge carriers. We find direct evidence for the induced moiré potential in the emergence of new excitonic resonances at integer fillings and our observation of an enhancement of the trion binding energy by <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mo>≃</e:mo><e:mn>3</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:mi>meV</e:mi></e:mrow></e:math>. A theoretical model for exciton-electron interactions allows us to directly determine the moiré potential modulation of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>30</g:mn><g:mo>±</g:mo><g:mn>5</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>meV</g:mi></g:math> from the measured trion binding energy shift. We obtain direct evidence for charge order linked to electronic Mott-Wigner states at filling factors <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>ν</i:mi><i:mo>=</i:mo><i:mn>1</i:mn><i:mo>/</i:mo><i:mn>3</i:mn></i:math> and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>ν</k:mi><k:mo>=</k:mo><k:mn>2</k:mn><k:mo>/</k:mo><k:mn>3</k:mn></k:math> through the associated exciton umklapp resonances.