Gate-dependent Pseudospin Mixing in Graphene/Boron Nitride Moire Superlattices

TL;DR

This study investigates how gate voltage influences pseudospin mixing in graphene/boron nitride Moire superlattices, revealing a tunable spinor potential that impacts electronic properties and device applications.

Contribution

It demonstrates that the pseudospin-mixing component of the Moire superlattice potential is gate-dependent and can be directly probed via infrared spectroscopy, advancing pseudospin control in 2D heterostructures.

Findings

Pseudospin-mixing potential acts like a spatially varying pseudomagnetic field.

Gate voltage significantly alters the spinor potential.

Electron-electron interactions strongly renormalize the pseudospin potential.

Abstract

Electrons in graphene are described by relativistic Dirac-Weyl spinors with a two-component pseudospin1-12. The unique pseudospin structure of Dirac electrons leads to emerging phenomena such as the massless Dirac cone2, anomalous quantum Hall effect2, 3, and Klein tunneling4, 5 in graphene. The capability to manipulate electron pseudospin is highly desirable for novel graphene electronics, and it requires precise control to differentiate the two graphene sub-lattices at atomic level. Graphene/boron nitride (graphene/BN) Moire superlattice, where a fast sub-lattice oscillation due to B-N atoms is superimposed on the slow Moire period, provides an attractive approach to engineer the electron pseudospin in graphene13-18. This unusual Moire superlattice leads to a spinor potential with unusual hybridization of electron pseudospins, which can be probed directly through infrared spectroscopy because optical transitions are very sensitive to excited state wavefunctions. Here, we perform micro-infrared spectroscopy on graphene/BN heterostructure and demonstrate that the Moire superlattice potential is dominated by a pseudospin-mixing component analogous to a spatially varying pseudomagnetic field. In addition, we show that the spinor potential depends sensitively on the gate-induced carrier concentration in graphene, indicating a strong renormalization of the spinor potential from electron-electron interactions. Our study offers deeper understanding of graphene pseudospin structure under spinor Moire potential, as well as exciting opportunities to control pseudospin in two-dimensional heterostructures for novel electronic and photonic nanodevices.