NLoptics on nanoclusters

[dagosta]

Dear All,

can one use yambo_nl to perform pump and probe calculations of spectra of nano-clusters?

A fast attempt returned essentially nothing -- no polarization at all, and I am then wondering if I am missing something.

Thanks.

Best regards,
Roberto

[claudio]

Dear Roberto

yambo_nl used the Berry formulation for the coupling with the external field, through the numerical derivative in k of the wave-functions.
Therefore it works only when k-points are present. It is true that it exist a formulation of the Berry Polarization at Gamma point,
(see Resta Notes) but we did not implemented it and it converges very slowly with the cell size.

You can try to do pump and probe by using standard dipoles with the flag: UseDipoles
You can find this flag generating input with -V nl verbosity.
Anyway these dipole do not include intra-bands terms, that could be not so important in your case.

Otherwise in Yambo are also implemented dipole as integral in real-space that are suitable for isolated systesm,
using yambo_rt. Maybe Davide can say you more on this implementation

best
Claudio