Quantum phase transitions in interfacing two gapped systems of ordinary fermions driven by external strain and atomic adsorption.

We study how the electronic structure of a single bilayer Bi on a single quintuple layer Bi₂Se₃ (Bi₂Te₃) changes with interface polarization, strain and H adsorption using first-principles calculations. We find that for strained systems the Dirac cone state does not show in the band gap. Coupled with strain and H adsorption, the six spin-polarized Dirac cones in the band gap are created by the interfacing two gapped films. The internal electrical field can result in variations in the work function relative to Bi and Bi₂Se₃ surfaces. Our findings confirm that the interface polarization, strain and atomic adsorption are the effective means to manipulate electronic structures and topological states on non-metallic surfaces, which could be helpful for realizing atomically thin spintronic devices. [ABSTRACT FROM AUTHOR]