Topological phase stability and transformation of bismuthene

Two-dimensional topological materials, in the form of ultrathin films grown on substrates, are outstanding candidates for spintronic applications. Their electronic structures including the topological class can be tuned or altered by strain and isoelectronic substitutional alloying. First-principles calculations show that the topological order of a monolayer Bi, bismuthene, is unusually robust against strain and changes in spin-orbit coupling strength. The phase diagram shows a large area in which the system is a topological insulator; phase boundaries for transforming into other phases, trivial or not, are mapped out.