Engineering topological phase transitions via sliding ferroelectricity in MBi2Te4 (M = Ge, Sn, Pb) bilayers

TL;DR

This study demonstrates how sliding ferroelectricity in MBi2Te4 bilayers induces reversible topological phase transitions, enabling room-temperature quantum spin Hall effects and reconfigurable quantum devices through electric polarization control.

Contribution

It introduces a novel mechanism of topological phase control via sliding ferroelectricity in layered materials, combining first-principles calculations with topological analysis.

Findings

Reversible topological phase transitions achieved through interlayer sliding.

Room-temperature quantum spin Hall effect enabled by sizable spin-orbit gaps.

Strong out-of-plane ferroelectric polarization confirmed in MBi2Te4 bilayers.

Abstract

Materials combining electrically switchable ferroelectricity and tunable topological states hold significant promise for advancing both foundamental quantum phenomena and innovative device architectures. Here, we employ first-principles calculations to systematically investigate the sliding ferroelectricity-mediated topological transitions in bilayer MBi2Te4 (M = Ge, Sn, Pb). By strategically engineering interlayer sliding configurations with oppositely polarized states, we demonstrate reversible band inversion accompanied by topological phase transitions. The calculated spin-orbit-coupled bandgaps reach 31 meV (GeBi2Te4), 36 meV (SnBi2Te4), and 35 meV (PbBi2Te4), thereby enabling room-temperature observation of the quantum spin Hall effect. Crucially, these systems exhibit substantial out-of-plane ferroelectric polarization magnitudes of 0.571-0.623 pC/m, with PbBi2Te4 showing the maximum polarization (0.623 pC/m). The topological nontriviality is unambiguously confirmed by two independent signatures: (i) the computed z2 topological invariant, and (ii) the emergence of gapless helical edge states spanning the bulk insulating gap. This synergy arises from the unique sliding-induced charge redistribution mechanism, which simultaneously modulates Berry curvature and breaks in-plane inversion symmetry without disrupting out-of-plane polarization stability. The co-engineering of non-volatile ferroelectric switching and topologically protected conduction channels in MBi2Te4 bilayers establishes a material paradigm for designing reconfigurable quantum devices, where electronic topology can be electrically controlled via polarization reversal. Our results provide critical insights into manipulating correlated quantum states in van der Waals ferroelectrics for multifunctional nanoelectronics.