Electron Collimation in Twisted Bilayer Graphene via Gate-Defined Moiré Barriers.

Ren, Wei; Zhang, Xi; Zhu, Ziyan; Khan, Moosa; Watanabe, Kenji; Taniguchi, Takashi; Kaxiras, Efthimios; Luskin, Mitchell et al. · Nano Lett · 2024

basic_science · Level V

Where this comes from

Abstract

Electron collimation via a graphene p-n junction allows electrostatic control of ballistic electron trajectories akin to that of an optical circuit. Similar manipulation of novel correlated electronic phases in twisted-bilayer graphene (tBLG) can provide additional probes to the underlying physics and device components toward advanced quantum electronics. In this work, we demonstrate collimation of the electron flow via gate-defined moiré barriers in a tBLG device, utilizing the band-insulator gap of the moiré superlattice. A single junction can be tuned to host a chosen combination of conventional pseudo barrier and moiré tunnel barriers, from which we demonstrate improved collimation efficiency. By measuring transport through two consecutive moiré collimators separated by 1 μm, we demonstrate evidence of electron collimation in tBLG in the presence of realistic twist-angle inhomogeneity.