Zitterbewegung of moir\'e excitons in twisted MoS$_2$/WSe$_2$ hetero-bilayers

TL;DR

This paper demonstrates that moiré excitons in twisted MoS₂/WSe₂ hetero-bilayers exhibit zitterbewegung, a trembling motion analogous to Dirac particles, which can be experimentally observed and tuned via gating and twist angle.

Contribution

It reveals the presence of zitterbewegung in moiré excitons and discusses how their dynamics can be studied in van der Waals heterostructures with tunable parameters.

Findings

Moiré excitons in twisted hetero-bilayers exhibit zitterbewegung.

The zitterbewegung timescales are compatible with current experimental techniques.

The exciton dynamics can be tuned by gating and twist angle.

Abstract

The moir\'e pattern observed in stacked non-commensurate crystal lattices, such as hetero-bilayers of transition metal dichalcogenides, produces a periodic modulation of their bandgap. Excitons subjected to this potential landscape exhibit a band structure that gives rise to a quasi-particle dubbed moir\'e exciton. In the case of MoS$_2$/WSe$_2$ hetero-bilayers, the moir\'e trapping potential has honeycomb symmetry and, consequently, the moir\'e exciton band structure is the same as that of a Dirac-Weyl fermion, whose mass can be further tuned down to zero with a perpendicularly applied field. Here we show that, analogously to other Dirac-like particles, moir\'e exciton exhibits a trembling motion, also known as zitterbewegung, whose long timescales are compatible with current experimental techniques for exciton dynamics. This promotes the study of the dynamics of moir\'e excitons in van der Waals heterostructures as an advantageous solid-state platform to probe zitterbewegung, broadly tunable by gating and inter-layer twist angle.