Pablo Resendiz Vazquez

Pablo Resendiz Vazquez

Affiliation: Monash University

Research Interests: Topological Quantum Matter

Title: Electrostatic disorder in moiré band energies in marginally twisted bilayer MoS₂

Abstract: Moiré superlattices in twisted transition metal dichalcogenides (tTMDs) provide a versatile platform to engineer flatband structures that host correlated electronic phases which remain challenging to realize in conventional materials, such as generalized Wigner crystals or topologically non-trivial phases. While theory predicts a broad angular range over which such flatbands can exist, miniband characteristics are influenced not only by stacking geometry and symmetry of the moiré superlattice but also by disorder, which is ubiquitous in these systems and can strongly reshape the miniband electronic landscape. Yet, its impact remains an open question.
We used scanning tunnelling spectroscopy to study how electrostatic disorder reshapes the character of the minibands of marginally twisted bilayer MoS₂ (θ ≃ 0.9°). Our measurements reveal an unexpected 15 ± 4 meV shift in the valence band onset regions with local MX and XM stacking (referring to the vertical arrangement of M = Mo, X = S atoms), which is unexpected due to symmetry-based considerations. We also observe spatially correlated fluctuations of the band onset energies. We find that the correlated disorder in band onset energy can be understood in terms of a potential of random background charges, and infer an impurity charge density of a few 10¹¹ cm⁻². Continuum-model calculations of the minibands under electric fields consistent with the impurity charge density reveal the splitting of the first moiré miniband into MX- and XM-localized sub-bands, in agreement with experiment. These results demonstrate that even weak electrostatic disorder can redefine moiré miniband physics at low-energy scales, highlighting disorder as a decisive factor in the electronic landscape of marginally twisted transition metal dichalcogenides at the nanoscale.