Theoretical predicted topological properties of Janus SrInGaTe4

Abstract

Two-dimensional (2D) Janus structures have emerged as promising materials due to their novel physical properties and wide-ranging potential applications. The symmetry breaking inherent in Janus structures raises an intriguing question: do their topological properties persist despite this asymmetry? Both theoretically predicted Janus SrInGaTe₄ and its parent compound SrGa₂Te₄ retain their topological characteristics when spin-orbit coupling (SOC) is considered. Furthermore, Rashba-type spin splitting is observed at both the conduction band minimum (CBM) and the valence band maximum (VBM), attributed to the inversion asymmetry. The electronic properties of SrInGaTe₄ can be modulated using biaxial strain and external electric fields. Under a tensile strain of 6 %, the inverted band gap of SrInGaTe₄ increases significantly from 40 meV (at zero strain) to 124 meV. Similarly, an applied vertical electric field of 0.2V/Å enlarges the inverted band gap to 84 meV. Topological invariants (Z₂) calculations reveal that SrInGaTe₄ transitions to a normal insulator under a compressive strain of −2 %. Additionally, an applied electric field induces a topological phase transition from non-trivial to trivial, with a critical field of approximately −0.2V/Å. This study demonstrates that both strain and electric fields can effectively tune the topological properties of select 2D materials. These findings provide valuable insights for the design and development of advanced spintronic devices.