Observation of electrically tunable Feshbach resonances in twisted bilayer semiconductors

TL;DR

This paper reports the discovery of electrically tunable Feshbach resonances in twisted bilayer semiconductors, enabling control over exciton-hole interactions and opening new avenues for studying many-body physics optically.

Contribution

It introduces the observation of electrically tunable Feshbach resonances in twisted bilayer semiconductors, a novel phenomenon enabling control of inter-layer exciton-hole interactions.

Findings

Observation of electrically tunable 2D Feshbach resonance.

Control over exciton-hole interaction strength.

Potential for optical exploration of many-body physics.

Abstract

Moire superlattices in twisted transition metal dichalcogenide bilayers have emerged as a rich platform for exploring strong correlations using optical spectroscopy. Despite observation of rich Mott-Wigner physics stemming from an interplay between the periodic potential and Coulomb interactions, the absence of tunnel coupling induced hybridization of electronic states ensured a classical layer degree of freedom in these experiments. Here, we investigate a MoSe$_2$ homobilayer structure where inter-layer coherent tunnelling and layer-selective optical transitions allow for electric field controlled manipulation and measurement of the layer-pseudospin of the ground-state holes. A striking example of qualitatively new phenomena in this system is our observation of an electrically tunable 2D Feshbach resonance in exciton-hole scattering, which allows us to control the strength of interactions between excitons and holes located in different layers. Our findings enable hitherto unexplored possibilities for optical investigation of many-body physics, as well as realization of degenerate Bose-Fermi mixtures with tunable interactions, without directly exposing the itinerant fermions to light fields.