Pump and Probe
This tutorial works only with Yambo version > 5.0, that will be released soon.
In this tutorial we will show you how to setup two external fields in yambo_nl, to perform pump and probe simulation.
The input simulation parameters of these tutorial require large computational power,
we advice you to run them in parallel, or to use simplified parameters for example less bands, k-points and so on.
This tutorial supposes that you are already familiar with real-time simulation with Yambo,
if it is not the case please check these tutorials: Tutorials#Non_linear_response
We start from the bulk hBN with an in place lattice constant a=4.72431525 a.u. and c/a=2.6. Standard DFT input for hBN for ABINIT or QuantumEspresso can be found here Tutorials. We used 200 bands in the Non-self consistent calculation.
In our example we choose direction [0,1,0] for the pump and the probe. We generate the ypp.in to remove symmetries with the command ypp -y and we modify it as:
fixsyms # [R] Remove symmetries not consistent with an external perturbation % Efield1 0.000000 | 1.000000 | 0.000000 | # First external Electric Field % % Efield2 0.000000 | 1.000000 | 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
then we go in the FixSymm directory and run again the setup. Now we calculate collisions, since we want to include excitonic effects in the calculations. Using the command: yambo_nl -v h+sex+cvonly -e -X s:
collisions # [R] Collisions em1s # [R][Xs] Statically Screened Interaction dipoles # [R] Oscillator strenghts (or dipoles) DIP_Threads=0 # [OPENMP/X] Number of threads for dipoles X_Threads=0 # [OPENMP/X] Number of threads for response functions RT_Threads=0 # [OPENMP/RT] Number of threads for real-time Chimod= "HARTREE" # [X] IP/Hartree/ALDA/LRC/PF/BSfxc % BndsRnXs 1 | 200 | # [Xs] Polarization function bands % NGsBlkXs= 5000 mHa # [Xs] Response block size % LongDrXs 0.000000 | 1.000000 | 0.000000 | # [Xs] [cc] Electric Field % XTermKind= "BG" # [X] X terminator ("none","BG" Bruneval-Gonze) % COLLBands 5 | 12 | # [COLL] Bands for the collisions % HXC_Potential= "SEX+HARTREE+CVONLY" # [SC] SC HXC Potential HARRLvcs= 10000 mHa # [HA] Hartree RL components EXXRLvcs= 10000 mHa # [XX] Exchange RL components CORRLvcs= 10000 mHa # [GW] Correlation RL components
then we generate the Pump&Probe input with the command yambo_nl -u p -V rt:
nloptics # [R] Non-linear spectroscopy DIP_Threads=0 # [OPENMP/X] Number of threads for dipoles NL_Threads=0 # [OPENMP/NL] Number of threads for nl-optics % NLBands 3 | 6 | # [NL] Bands range % NLverbosity= "high" # [NL] Verbosity level (low | high) NLstep= 0.010000 fs # [NL] Time step length NLtime= 75.0000 fs # [NL] Simulation Time NLintegrator= "INVINT" # [NL] Integrator ("EULEREXP/RK2/RK4/RK2EXP/HEUN/INVINT/CRANKNIC") NLCorrelation= "IPA" # [NL] Correlation ("IPA/HARTREE/TDDFT/LRC/LRW/JGM/SEX") NLLrcAlpha= 0.000000 # [NL] Long Range Correction NLDamping= 0.100000 eV # [NL] Damping (or dephasing) RADLifeTime= 15.00000 fs # [RT] Radiative life-time (if negative Yambo sets it equal to Phase_LifeTime in NL) #UseDipoles # [NL] Use Covariant Dipoles (just for test purpose) #FrSndOrd # [NL] Force second order in Covariant Dipoles #EvalCurrent # [NL] Evaluate the current HARRLvcs= 10417 RL # [HA] Hartree RL components EXXRLvcs= 10417 RL # [XX] Exchange RL components % ExtF_Dir 1.000000 | 1.000000 | 0.000000 | # [NL ExtF] Field Versor % % ExtF_Freq 1.500000 | 1.500000 | eV # [NL ExtF] Field Frequency % ExtF_Int= 1000.00 kWLm2 # [NL ExtF] Field Intensity ExtF_Width= 5.00000 fs # [NL ExtF] Field Width ExtF_kind= "QSSIN" # [NL ExtF] Kind(SIN|SOFTSIN|RES|ANTIRES|GAUSS|DELTA|QSSIN) ExtF_Tstart= 0.010000 fs # [NL ExtF] Initial Time % ExtF2_Dir 0.000000 | 0.000000 | 1.000000 | # [NL ExtF] Field Versor % % ExtF2_Freq 0.100000 | 0.100000 | eV # [NL ExtF] Field Frequency % ExtF2_Int= 10.0000 kWLm2 # [NL ExtF] Field Intensity ExtF2_Width= 0.000000 fs # [NL ExtF] Field Width ExtF2_kind= "DELTA" # [NL ExtF] Kind(SIN|SOFTSIN|RES|ANTIRES|GAUSS|DELTA|QSSIN) ExtF2_Tstart= 30.00000 fs # [NL ExtF] Initial Time
In this simulation we set a dephasing of 0.1 eV and a radiative life-time of 15 fs, The two external field are a sinus with frequency 1.5 eV convoluted with a Guassian of width 5 fs with and intensity of 1000 KW/cm-2, and then a delta function that starts at 30 fs with an intensity of 10 KW/cm-2. Below we plot the external electric field in the x direction and the polarization in x and z directions:
