Unconventional spin momentum locking and topological domains in twisted slabs of topological insulator Bi 2 Te 3

The three-dimensional topological insulator Bi 2 Te 3 hosts topological Dirac states on its two-dimensional surfaces. These Dirac states show spin-momentum locking, which usually implies a tangential Rashba-like spin texture. One can alter the properties of the Dirac states by dividing a slab of such a material into two thinner halves, modifying the interface by twisting, shifting, and changing the interlayer distance. Using first-principles calculations, we investigate such modified slabs of Bi 2 Te 3. The twisting degree of freedom deserves special attention. To this end, we follow two approaches. On the one hand, we probe different stacking configurations in order to extract parameters relevant for small twist angle Moiré structures. We find non-trivial topology only for some stackings, leading to topological domains on the Moiré scale. On the other hand, we calculate the properties of commensurate twisted supercells. The latter reveals not only flat bands, which are tunable by external pressure, but also radial spin textures with unconventional spin-momentum locking.