Interfacial ferroelectricity by van der Waals sliding

• Published in: Science (American Association for the Advancement of Science) Vol. 372; no. 6549; pp. 1462 - 1466
• Main Authors: Vizner Stern, M, Waschitz, Y, Cao, W, Nevo, I, Watanabe, K, Taniguchi, T, Sela, E, Urbakh, M, Hod, O, Ben Shalom, M
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 25.06.2021
• Subjects: Atomic force microscopy; Boron; Crystals; Ferroelectricity; Polarization
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abe8177

Despite their partial ionic nature, many layered diatomic crystals avoid internal electric polarization by forming a centrosymmetric lattice at their optimal 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 provide intuitive insights to explore the interfacial polarization and its unique "slidetronics" switching mechanism.