Field-Tunable Valley Coupling and Localization in a Dodecagonal Semiconductor Quasicrystal

TL;DR

This study demonstrates how a dodecagonal WSe2 quasicrystal enables tunable valley coupling and localization effects through atomic arrangement and electric fields, revealing new possibilities for valleytronics.

Contribution

It uncovers how quasicrystal atomic arrangements facilitate momentum space proximity of valleys and induce hybridization and localization, advancing valley engineering techniques.

Findings

Electric field induces strong interlayer K-Q hybridization.

Disappearance of trion resonance due to localization.

Valleys can be brought arbitrarily close in momentum space.

Abstract

Quasicrystals are characterized by atomic arrangements possessing long-range order without periodicity. Van der Waals (vdW) bilayers provide a unique opportunity to controllably vary atomic alignment between two layers from a periodic moir\'e crystal to an aperiodic quasicrystal. Here, we reveal a remarkable consequence of the unique atomic arrangement in a dodecagonal WSe2 quasicrystal: the K and Q valleys in separate layers are brought arbitrarily close in momentum space via higher-order Umklapp scatterings. A modest perpendicular electric field is sufficient to induce strong interlayer K-Q hybridization, manifested as a new hybrid excitonic doublet. Concurrently, we observe the disappearance of the trion resonance and attribute it to quasicrystal potential driven localization. Our findings highlight the remarkable attribute of incommensurate systems to bring any pair of momenta into close proximity, thereby introducing a novel aspect to valley engineering.