Exciton-phonon coupling and luminescence: Difference between revisions
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#KeepKGrid # Do not expand the k-grid | #KeepKGrid # Do not expand the k-grid | ||
the code will expand the electronic wave-function and copy the ''gkkp_expanded'' databases in the new folder. | the code will expand the electronic wave-function and copy the ''gkkp_expanded'' databases in the new folder.<br> | ||
'''BSE at finite momentum''':<br> | |||
Go in the folder without symmetries, run the setup, perform the GW calculation if required from your system, and then run the BSE for all momentum '''q''' | |||
as explained in the tutorial: | |||
== References == | == References == | ||
Revision as of 11:07, 21 February 2022
This tutorial works only with Yambo version > 6.x
The exciton-phonon part of Yambo does not support symmetries yet!!!
This an advanced tutorial, in order to calculate exciton-phonon coupling and phonon-assisted absorption/emission you need a deep knowledge of the theory and of the Yambo code.
In this tutorial we will calculate phonon-assisted absorption and luminescence including the scattering between exciton and phonon.[1][2][3]
We will consider as example bulk silicon. Notice that parameters of the present tutorial are not at convergence, but are just as a possible example.
The tutorial includes several steps and the calculations can be quite expensive.
Electron-phonon matrix elements:
First of all we calculate electron-phonon matrix elements as explained in the section: Electron-phonon matrix elements but in the last passage of the tutorial we expand the electron-phonon matrix elements in all the Brillouin Zone. In order to do so, when we read the electron-phonon matrix elements from QE with the command ypp_ph -g g we turn on the flag GkkpExpand
gkkp # [R] gkkp databases gkkp_db # [R] GKKP database #GkkpReadBare # Read the bare gkkp DBsPATH= "../elph_dir/" # Path to the PW el-ph databases PHfreqF= "none" # PWscf format file containing the phonon frequencies PHmodeF= "none" # PWscf format file containing the phonon modes GkkpExpand # Expand the gkkp in the whole BZ #UseQindxB # Use qindx_B to expand gkkp (for testing purposes)
if everything worked fine in the log you will find:
.... <---> :: Uniform sampling :yes <---> :: Symmetry expanded :yes .....
Notice that in the calculation of the electron-phononn coupling you need a number of conduction bands as large as the one that will be used in the Bethe-Salpeter Equation.
Remove all symmetries:
Now we remove all symmetries with the command ypp_ph -y
fixsyms # [R] Remove symmetries not consistent with an external perturbation
% Efield1
0.000000 | 0.000000 | 0.000000 | # First external Electric Field
%
% Efield2
0.000000 | 0.000000 | 0.000000 | # Additional external Electric Field
%
BField= 0.000000 T # [MAG] Magnetic field modulus
Bpsi= 0.000000 deg # [MAG] Magnetic field psi angle [degree]
Btheta= 0.000000 deg # [MAG] Magnetic field theta angle [degree]
RmAllSymm # Remove all symmetries
#RmTimeRev # Remove Time Reversal
#RmSpaceInv # Remove Spatial Inversion
#KeepKGrid # Do not expand the k-grid
the code will expand the electronic wave-function and copy the gkkp_expanded databases in the new folder.
BSE at finite momentum:
Go in the folder without symmetries, run the setup, perform the GW calculation if required from your system, and then run the BSE for all momentum q
as explained in the tutorial:
References
- ↑ Theory of phonon-assisted luminescence in solids: Application to hexagonal boron nitride, E. Cannuccia, B. Monserrat and C. Attaccalite, Phys. Rev. B 99, 081109(R) (2019)
- ↑ Exciton-Phonon Coupling in the Ultraviolet Absorption and Emission Spectra of Bulk Hexagonal Boron Nitride, F. Paleari et al. PRL 122, 187401(2019)
- ↑ Exciton-Phonon Interaction and Relaxation Times from First Principles, Hsiao-Yi Chen, Davide Sangalli, and Marco Bernardi,Phys. Rev. Lett. 125, 107401(2020)