EPW Forum

Dear developers and users,

I have a question about the names used for the vme flag in EPW v5.4. According to the documentation,
vme = 'dipole' computes the velocity as dipole+commutator = <psi_mk|p+i[V_NL,r]|psi_nk>
vme = 'wannier' computes the velocity as dH_nmk/dk - i(e_nk-e_mk)A_nmk where A is the Berry connection.

In this explanation, I think that the "p" operator is called "dipole". But I am confused because "dipole" often also refers to the position operator. Coincidentally, the position matrix element is related to the Berry connection, so I often get confused and think that "dipole" refers to using the Berry connection.

I'm not suggesting to change the names.
I'm asking if you there is any explanation about the naming that I am missing.

Regards,
Jae-Mo Lihm
Seoul National University

Dear Jae-Mo Lihm:

There was a suggestion for this naming during our meeting, but I think that there is no specific reason for this naming;

In older versions, the matrix elements of the operator p was called "dipole" in the code and even if now these matrix elements include non-local corrections, the same name is used for backward compatibility.

Sincerely,

H. Lee