## HOTNANO project meeting 21-04-2022

1) For TCI phase: Which model to use for numerical implementation? How to break the symmetries to achieve HOTI phase?

2) Corners are not perfect but rounded (couple of atoms), would that change the nature of hinge modes?

3) What would happen if one goes thinner with TCI, would you get a new phase? I suspect that one should get QSHI phase.

4) Depending on the number of Dirac cones (1 or 2) for the thin film, then you can get QSHI (for 1) or another phase (QSHI-like) but protected by mirror symmetry.
Max: "if its (111) on facet then 2Dirac cones, if (100) then 1"

5) How thin can SnTe films get? SnTe on PbTe 10 nm thick. On InP, 40 nm. Can decrease further.

6) What would be the typical surface charge density to screen the effect of the electric field so that bulk stays insulating? The electric field is for the HOTI phase.

7) What would happen if we tilt the surfaces around the mirror plane? Would we get hinge modes? Should we break the bulk symmetries?

8) Substrate introduces dislocation and a bit of strain (decays almost instantly). What would happen to the surface states?

9) 3D QSHI (helical hinge modes in 3D). We can use such system to come up with a design that would make the heat turn a corner.

10) Infer $v_F$ of the hinge states from a minimal model (finding the band gap should be enough). This is related to Maxwell's demon idea with hinge modes.