Thickness-dependent topological phase transition and Rashba-like preformed topological surface states of α-Sn(001) thin films on InSb(001)

Topological materials, possessing spin-momentum locked topological surface states (TSS), have attracted much interest due to their potential applications in spintronics. alpha-phase Sn (alpha-Sn), being one of them, displays enriched topological phases via band-gap engineering through a strain or confinement effect. In this work, we investigated the band evolution of in-plane compressively strained alpha-Sn(001) thin films on InSb(001) in a wide range of thickness from 3 bilayers (BL) to 370 BL by combining angle-resolved photoemission spectra and first-principles calculations. Gapped surface states evolved to a linearly dispersive TSS at a critical thickness of 6 BL, indicating that the system undergoes a phase transition from topologically trivial to nontrivial. For films thicker than 30 BL, additional Rashba-like surface states (RSS) were identified. These RSS served as preformed TSS in another strain-induced topological phase transition. In thick films, 370-BL alpha-Sn(001), so as to preclude the confinement effect in thin films, our results were consistent with a Dirac semimetal phase with Dirac nodes located along Gamma-Z. This thickness-dependent band-structure study deepens our understanding of topological phase transitions and the evolution of Dirac states. Furthermore, the coexistence of TSS and RSS in a Dirac semimetal alpha-Sn might significantly enhance the potential for spintronic applications.

Automated summary

Topological material α-Sn exhibits rich topological phases and its band structure is influenced by strain and confinement effects. Researchers found that the gapped surface states of α-Sn transformed into linearly dispersive TSS at a critical thickness of 6 bilayers (BL), indicating a phase transition from trivial to nontrivial. Additional Rashba-like surface states (RSS) were identified in films thicker than 30 BL, serving as preformed TSS in another strain-induced topological phase transition. In thick films of 370 BL, α-Sn displayed a Dirac semimetal phase with Dirac nodes located along Gamma-Z. This thickness-dependent band structure study deepens the understanding of topological phase transitions and the evolution of Dirac states, and the coexistence of TSS and RSS in α-Sn may significantly enhance its potential for spintronic applications.