F\"orster valley-orbit coupling and topological lattice of hybrid moir\'e excitons

TL;DR

This paper demonstrates how F"orster coupling in hybrid moiré excitons enables coherent hopping and topological phases, offering new ways to manipulate valley-orbit interactions in 2D semiconductor superlattices.

Contribution

It reveals the significant role of F"orster valley-orbit coupling in altering moiré exciton properties and inducing topological phases in twisted TMD heterostructures.

Findings

F"orster coupling enables coherent exciton hopping over 10 nm

Valley-flip channels are as significant as valley-conserving ones

Topological phase diagram arises from valley-orbit coupling in twisted MoTe2

Abstract

Hybrid exciton in moir\'e superlattices of two-dimensional (2D) semiconductors inherits the electric dipole, strong moir\'e trapping, and stacking optical selection rules from its interlayer part, whereas the intralayer part is intended for enhancing optical coupling strength. Here, we show that electron-hole Coulomb exchange, or F\"orster coupling, within the intralayer component qualitatively alters the properties of moir\'e excitons, enabling their coherent hopping between moir\'e traps laterally separated over 10 nm and/or across layers, where their kinetic propagation is completely suppressed. Valley-flip hopping channels are found as significant as the valley-conserving ones, leading to rich possibilities to tailor valley-orbit-couplings and introduce non-trivial topology to the moir\'e exciton superlattice. In twisted MoTe$_2$ where hybrid moir\'e excitons feature a symmetry protection from radiative recombination, we show that F\"orster valley-orbit-coupling can give rise to a rich topological phase diagram.