Inversion Symmetry Breaking in Epitaxial Ultrathin Bi (111) Films

TL;DR

This study investigates ultrathin Bi (111) films grown on InSb substrates, revealing inversion symmetry breaking and clarifying their topological triviality, which impacts their potential in spintronics and topological applications.

Contribution

It demonstrates that epitaxial growth induces inversion symmetry breaking in Bi (111) films and resolves the topological nature of their surface states, challenging previous assumptions.

Findings

Surface states are topologically trivial.

Interfacial bonds prevent semimetal-to-semiconductor transition.

Epitaxial stabilization influences topological properties.

Abstract

Bismuth (Bi) films hold potential for spintronic devices and topological one-dimensional edge transport. Large-area high-quality (111) Bi ultrathin films are grown on InSb (111)B substrates. Strong film-substrate interactions epitaxially stabilize the (111) orientation and lead to inversion symmetry breaking. We resolve the longstanding controversy over the Z_2 topological assignment of bismuth and show that the surface states are topologically trivial. Our results demonstrate that interfacial bonds prevent the semimetal-to-semiconductor transition predicted for freestanding bismuth layers, highlighting the importance of controlled functionalization and surface passivation in two-dimensional materials.