Layer k-projection and unfolding electronic bands at interfaces

TL;DR

This paper introduces a k-projection and unfolding method for electronic band structures at interfaces, enabling detailed analysis of heterostructures and their experimental connections.

Contribution

The authors develop an efficient unfolding technique using k-projection to analyze local band structures in heterostructures and interfaces, enhancing interpretation of complex systems.

Findings

Graphene bilayer band structure depends on SiC termination

Magnetic proximity induces spin splitting in BAs/CrI3

Silicene on Ag(111) reproduces ARPES results and clarifies non-Dirac states

Abstract

The k-projection method provides an approach to separate the contributions from different constituents in heterostructure systems and can act as an aid to connect the results of experiments and calculations. We show that the technique can be used to "unfold" the calculated electronic bands of interfaces and supercells, and provide local band structure by integrating the projected states over specified regions of space, a step that can be implemented efficiently using fast Fourier transforms. We apply the method to investigate the effects of interfaces in heterostructures consisting of a graphene bilayer on H-saturated SiC(0001), BAs monolayer on the ferromagnetic semiconductor CrI3, silicene on Ag(111), and to the Bi2Se3 surface. Our results reveal that the band structure of the graphene bilayer around the Dirac point is strongly dependent on the termination of SiC(0001): on the C face, the graphene is n doped and a gap of ~0.13 eV is opened, whereas, on the Si face, the graphene is essentially unchanged and neutral. We show that for BAs/CrI3, the magnetic proximity effect can effectively induce a spin splitting up to about 50 meV in BAs. For silicene/Ag(111), our calculations reproduce the angle-resolved photoemission spectroscopy results, including linearly dispersing bands at the edge of the first Brillouin zone of Ag(111); although these states result from the interaction between the silicene overlayer and the substrate, we demonstrate that they are not Dirac states.