Conductivity Outputs (.dat files)

Xatu computes the optical conductivity spectrum using both the independent-particle approximation (IPA) and the full Bethe-Salpeter equation (BSE). These are written to separate files during execution with the -a --absorption flag, provided that a valid kubo_w.in file is present.

Files Generated

Three output files are created, tipically defined in kubo_w.in as:

• *_sp.dat : IPA (independent-particle) optical conductivity

• *_ex.dat : BSE (excitonic) optical conductivity

• *_osc.dat: Exciton oscillator strengths (see Exciton Oscillator Strengths (_osc.dat))

Structure of *_sp.dat and *_ex.dat

Each file contains real parts of the conductivity tensor components for different photon energies:

omega  xx   xy   xz   yx   yy   yz   zx   zy   zz
.
.
.

Units

• \(\omega\) : photon energy in electron volts (eV)

• ij is \(Re[{\sigma_{ij}}]\) : real part of optical conductivity in units of \(e^{2}/\hbar\)

Post-processing

These .dat files can be plotted directly using absorption.py at /plot/ folder in Xatu repository.

Related Files

For oscillator strengths used in the excitonic conductivity calculation, see:

Exciton Oscillator Strengths (_osc.dat)