Controllable topological phase transition via ferroelectric-paraelectric switching in ferromagnetic single-layer MIMIIGe2X6 family

Abstract

Recently, the emergence of two-dimensional (2D) multiferroic materials has opened a new perspective for exploring topological states. However, instances of tuning topological phase transitions through ferroelectric (FE) polarization in 2D ferromagnetic (FM) materials are relatively rare. Here, we found that 11 single layer (SL) materials, namely the MIMIIGe2X6 family, possess both FE and FM properties. Among them, 5-SL materials exhibit controllable topological phase transition via ferroelectric-paraelectric switching. Taking SL ReIrGe2S6 as an example, we find that the paraelectric (PE) and FE phases exhibit half-metal and magnetic semiconductor behavior, respectively. In the spin-down channel of the PE phase, a critical-type Weyl point (WP) is observed with a robust Fermi arc edge state. In contrast, the FE phase of SL ReIrGe2S6 clearly identifies 0D corner states in both spin channels. Therefore, under the control of external fields, SL ReIrGe2S6 undergoes a transformation from PE to FE by overcoming the energy barrier of 0.62 eV, subsequently realizing the phase transition from the Weyl semimetal to the high order topological insulator. These findings greatly enrich research on 2D topological multiferroic materials and pave the way for the experimental discovery of 2D tunable topological phase transition.