[Wannier] Matrix elements of the Hamiltonian

[Md. Fhokrul Islam]

Dear developers and users,

I have recently started to use Wannier90 code and I am wondering if someone can help me clarify some confusions.

I am working with periodic systems. With spin-orbit coupling, the matrix elements of the Hamiltonian are, in general, expected to be complex except for the diagonal terms. But without spin-orbit, can the matrix element also be complex? Most of my calculations without spin-orbit show that the matrix elements are real. But one of my most recent calculations shows the elements are complex. So, I am wondering if it is correct or the result of some numerical error? In this case the system doesn't have inversion symmetry. Could it could be that since the DFT basis set are complex without inversion symmetry, and so the matrix elements of the Wannier90 Hamiltonian are also complex?

Also, is it possible to obtain complex matrix elements even with inversion symmetry and without spin-orbit coupling if disentanglement procedure is not done properly?


Regards,
Fhokrul
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