Intertwined Rashba, Dirac and Weyl Fermions in Hexagonal Hyperferroelectrics

TL;DR

This study uses density functional theory to explore spin-orbit coupling effects in hyperferroelectrics, revealing complex phenomena like Rashba effects, topological insulator phases, and Weyl semimetal states with potential spintronic applications.

Contribution

It uncovers the interplay of ferroelectricity and topological phases in hyperferroelectrics, including electric control of Rashba effects and the prediction of Weyl semimetal states.

Findings

Electric control of Rashba effect demonstrated

Existence of three-dimensional topological insulator phase

Weyl semimetal phase predicted after alloying

Abstract

By means of density functional theory based calculations, we study the role of spin-orbit coupling in the new family of ABC hyperferroelectrics [Phys. Rev. Lett. 112, 127601 (2014)]. We unveil an extremely rich physics strongly linked to ferroelectric properties, ranging from the electric control of bulk Rashba effect to the existence of a three dimensional topological insulator phase, with concomitant topological surface states even in the ultrathin film limit. Moreover, we predict that the topological transition, as induced by alloying, is followed by a Weyl semi-metal phase of finite concentration extension, which is robust against disorder, putting forward hyperferroelectrics as promising candidates for spin-orbitronic applications.