Electron-phonon coupling in twisted bilayer transition metal dichalcogenides using a hybrid classical/quantum mechanical approach

Incorporating the rotational degree of freedom into 2D heterostructures brought about a plethora of emergent physics including unconventional transport and superconductivity. To engineer twisted bilayer devices with desirable transport properties, studying the twist angle and layer dependence of electron-phonon coupling (EPC) is crucial. EPC in twisted bilayers of transition metal dichalcogenides (TMDs), where tentative signatures of superconductivity [1] are observed, remains largely unexplored.

Computing the electronic and vibrational properties of twisted bilayer TMDs from first-principles is challenging, due to their large superlattice sizes at small twist angles, coupled with the unfavourable system-size scaling of conventional first-principles methods. In this work, we present a hybrid classical/quantum mechanical approach that overcomes these limitations: for the electronic structure we use accurate and efficient first-principles tight-binding (TB) models [2]; and for vibrational properties, we use classical interatomic potentials that have been fitted to density-functional theory calculations. We incorporate position dependence into our TB model to study the electron-phonon coupling and related properties in selected twisted TMD bilayers and assess the accuracy of our hybrid approach against fully first-principles calculations at large twist angles.

[1] Wang L. et al., Nat. Mat. 19, pages 861–866 (2020)

[2] Vitale, V., Atalar, K., et al. 2D Materials 8, 4 (2021)