Delocalization of Quasiparticle Moir\'e States in Twisted Bilayer hBN

TL;DR

This paper investigates how quasiparticle states in twisted bilayer hBN are delocalized due to long-range interactions, revealing complex band gap variations and hybridization effects that depend on the twist angle.

Contribution

It demonstrates that non-local interactions significantly influence quasiparticle states in large twisted bilayer hBN, challenging the adequacy of local stacking models.

Findings

Band gap shows multiple minima with variable depth depending on twist angle.

Band-edge quasiparticle hybridization is suppressed at intermediate angles.

Degeneracy of minima occurs at the smallest twist angle studied.

Abstract

Twisted bilayers host many emergent phenomena in which the electronic excitations (quasiparticles - QPs) are closely intertwined with the local stacking order. By inspecting twisted hexagonal boron nitride (t-hBN), we show that non-local long-range interactions in large twisted systems cannot be reliably described by the local (high-symmetry) stacking and that the band gap variation (typically associated with the moir\'e excitonic potential) shows multiple minima with variable depth depending on the twist angle. We investigate twist angles of 2.45$^\circ$, 2.88$^\circ$, 3.48$^\circ$ and 5.09$^\circ$ using the GW approximation together with stochastic compression to analyze the QP state interactions. We find that band-edge QP hybridization is suppressed for intermediate angles which exhibit two distinct local minima in the moir\'e potential (at AA region and saddle point (SP)) which become degenerate for the largest system (2.45$^\circ$).