Valley Order and Loop Currents in Graphene on Hexagonal Boron Nitride

TL;DR

This paper investigates how Coulomb interactions induce exotic ordered states, including loop currents and spin-valley order, in graphene on hexagonal boron nitride, revealing potential experimental detection methods.

Contribution

It demonstrates that Coulomb interactions cause spontaneous chiral loop currents and spin-valley order in graphene on hBN, a novel state arising from substrate-induced superlattice effects.

Findings

Coulomb interactions induce chiral loop currents in graphene on hBN.

A macroscopic spin-valley order emerges at zero temperature.

Time reversal symmetry is broken in the resulting state.

Abstract

In this letter, we examine the role of Coulomb interactions in the emergence of macroscopically ordered states in graphene supported on hexagonal boron nitride substrates. Due to incommensuration effects with the substrate, graphene can develop gapped low energy modes that spatially conform into a triangular superlattice of quantum rings. In the presence of these modes, we show that Coulomb interactions lead to spontaneous formation of chiral loop currents in bulk and to macroscopic spin-valley order at zero temperature. We show that this exotic state breaks time reversal symmetry and can be detected with interferometry and polar Kerr measurements.