We use density functional theory (DFT) to study the topological properties of SnSe/EuS(111), HgTe/CdTe(001), and InAs/GaSb(001) interfaces. For the interface between the topological crystalline insulators SnSe and the magnetic insulator EuS, we find that a gap opens in the topological state at the interface, due to the magnetic proximity effect, which breaks the time reversal symmetry [PRM 4, 034203 (2020)]. For the HgTe/CdTe and InAs/GaSb interfaces we use DFT with a machine-learned Hubbard U correction [npj Computational Materials<i> </i>6, 180 (2020)] to examine whether a a two-dimensional topological insulator (2DTI) phase may be obtained. For the HgTe/CdTe interface, we find that band crossing is achieved and an inverted gap is obtained at a critical thickness of HgTe, in agreement with experiment. In contrast, for InAs/GaSb the gap narrows with increasing thickness of InAs; however the gap does not close for interfaces with up to 50 layers (about 15 nm) of each material. When an external electric field is applied across the InAs/GaSb interface, the GaSb-derived valence band maximum is shifted up in energy with respect to the InAs-derived conduction band minimum until eventually the bands cross and an inverted gap opens. Our results show that it may be possible to reach the topological regime at the InAs/GaSb interface. However, it may be challenging to realize the necessary conditions experimentally, which explains the difficulty of experimentally demonstrating an inverted gap in InAs/GaSb.

First principles simulations of topological interfaces

ACS Spring Meeting 2021

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