Interfacial Ferroelectricity by van-der-Waals Sliding

TL;DR

This paper demonstrates a novel ferroelectric order at the interface of hexagonal-boron-nitride flakes caused by lateral sliding, revealing potential for new 'slidetronics' applications through reversible polarization switching.

Contribution

It reports the discovery of interfacial ferroelectricity in naturally-grown h-BN flakes due to lateral stacking shifts, a phenomenon not previously observed in such materials.

Findings

Reversible polarization switching achieved by scanning a biased tip.

Alternating domains of inverted polarization observed at the interface.

Theoretical analysis links the effect to charge redistribution and ionic displacement.

Abstract

Despite their ionic nature, many layered diatomic crystals avoid internal electric polarization by forming a centrosymmetric lattice at their optimal anti-parallel van-der-Waals stacking. Here, we report a stable ferroelectric order emerging at the interface between two naturally-grown flakes of hexagonal-boron-nitride, which are stacked together in a metastable non-centrosymmetric parallel orientation. We observe alternating domains of inverted normal polarization, caused by a lateral shift of one lattice site between the domains. Reversible polarization switching coupled to lateral sliding is achieved by scanning a biased tip above the surface. Our calculations trace the origin of the phenomenon to a subtle interplay between charge redistribution and ionic displacement, and our minimal cohesion model predicts further venues to explore the unique "slidetronics" switching.