Dear all,
I am writing a real-time propagation code that requires high accuracy of
the the Berry connection matrix A_{nm}(k) = i <u_n|d_k u_m> in the
Hamiltonian gauge, which is e.g. given in WYSV2006 Eq.(25) and depends
on A in the Wannier gauge. However, in the calculation of the Berry
connection matrix in the Wannier gauge (get_oper.F90), it is mentioned
that this quantity is not Hermitian and Hermiticity is explicitly forced:
/"//Since Eq.(44) WYSV06 does not preserve the Hermiticity of the Berry
potential matrix, take Hermitean part (whether this makes a difference
or not for e.g. the AHC, depends on which expression is used to evaluate
the Berry curvature.//See comments in berry_wanint.F90)"/
I believe that this step introduces some small error, which is reflected
in my final results. I also cannot find the mentioned file
berry_wanint.F90. I am wondering if there are some ways to solve this
problem, i.e. by making the Berry connection matrix naturally Hermitian?
Any help or references is appreciated.
Best regards,
Lun Yue
Louisiana State University
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