Intertwined Hyperferroelectricity, Tunable Multiple Topological Phases and Giant Rashba Effect in Wurtzite LiZnAs

TL;DR

This paper demonstrates a unified framework in LiZnAs for intertwined hyperferroelectricity, multiple topological phases, and giant Rashba effects, revealing new pathways for spintronics and nonvolatile applications through first-principles calculations.

Contribution

It introduces a novel approach to achieve intertwined hyperferroelectricity, topological phases, and Rashba effects in LiZnAs using symmetry and spin-orbit coupling, supported by first-principles analysis.

Findings

Stable hyperferroelectricity with significant polarization.

Induction of Weyl semimetal and topological insulator phases via biaxial strain.

Reversal of spin textures through polarization switching.

Abstract

Composite quantum compounds offer a fertile ground for uncovering the complex interrelations between seemingly distinct phenomena in condensed matter physics for advanced nonvolatile and spintronics applications. Beyond topological superconductors and axion insulators, the idea of intertwined Hyperferroelectricity (HyFE), multiple topological phases and Rashba spin-splitting with reversible spin textures represents the local, global and symmetry-driven characteristics of quantum materials, respectively, offering unique pathways for enhanced functionalities. We unveiled a unified framework to achieve this synergy through the presence of crystalline symmetries and spin-orbit coupling in LiZnAs compound using first-principles calculations. HyFE exhibits ability to maintain spontaneous polarization under open-circuit boundary conditions, even with existence of depolarization field while Rashba effect exhibits paradigmatic spin texture in momentum space with tangential vector field. The presence of unstable $A_{2u}(LO)$ mode leads to free energy minimum with significant well depth and polarization of -66 meV and $P_{HyFE} = 0.282~C/m^2$, respectively indicating stable HyFE. The robust HyFE stem from mode-specific effective charges and larger high-frequency dielectric constants. This study also addresses the subtle question of whether critical point of topological phase transition shifts in response to drastically different Rashba spin-splitting values obtained from VASP and WIEN2k. Moreover, biaxial strain (BAS) induced Weyl semimetal (at 3.4% BAS) and topological insulating phase (after 3.4% BAS) is observed with giant Rashba coefficient of 5.91 eV {\AA} and 2.42 eV {\AA}, respectively. Furthermore, switching of bulk polarization leads to spin texture reversal, providing a robust mechanism to leverage spin degrees of freedom in these Hyperferroelectric Rashba topological materials.