Real-time dynamics with external field read from file
In this tutorial we will see how to generate an external field in a format compatible with Lumen and then use it to run real-time simulation (see for instance Ref. [1].
We will also prove a simple python script to do it, that you can easily modify to create your own external field.
The tutorial is divided in three sections: 1) generate external field with YamboPy, 2) generate external field with ypp_rt 3) use the external field in the real-time calculations.
Generate external field with YamboPy
Generate external field with ypp_rt
With ypp_rt one can generate all external fields that implemented in the Yambo code in the file src/modules/mod_fields.F. This can be usefull to visualize external fields used in Yambo without the need of running a real simulation. However if you want to add a new external field you have to code it in the file src/modules/mod_fields.F. The command to generate external field on file is: ypp_rt -rtplot f. This will generate the following input file:
TDplots # [R] TD observables plot RTtime # [R] Post-Processing kind: function of time RTfields # [R] Analize time-dependent fields TimeStep= 0.010000 fs # Time step % TimeRange 0.000000 |100.000000 | fs # Time-window where processing is done % % EnRngeRt 0.00000 | 20.00000 | eV # Energy range % ETStpsRt= 200 # Total Energy steps ChirpFac= 0.000000 fs # Prefactor for linear chirping in frequency space Field1_Freq= 2.000000 eV # [RT Field1] Frequency Field1_Int= 1000.000000 kWLm2 # [RT Field1] Intensity Field1_Width= 0.000000 fs # [RT Field1] Width Field1_kind= "SIN" # [RT Field1] Kind(SIN|COS|RES|ANTIRES|GAUSS|DELTA|QSSIN) Field1_pol= "linear" # [RT Field1] Pol(linear|circular) % Field1_Dir 1.000000 | 0.000000 | 0.000000 | # [RT Field1] Versor % Field1_Tstart= 0.010000 fs # [RT Field1] Initial Time
In the input file you have to specify a series of parameters, in red: the time step (TimeSpep), the time range (TimeRange), the field intensity (Field1_Int), the field kind (Field1_kind), its polarization, the field direction (Field1_Dir) and its starting time (Field1_Tstart), usually the first step of the dynamics. Then you run ypp_rt with this input and it will produce a series of files: YPP_EXTFIELD1_P1.time, YPP_EXTFIELD1_P2.time, YPP_EXTFIELD1_P1.freq, YPP_EXTFIELD1_P2.freq.
These files contain the external field and its Fourier transform. In the next section we will see how to use them in real-time dynamics.
Use generated external field with yambo_rt/yambo_nl
References
- ↑ D. Sangalli, Excitons and carriers in transient absorption and time-resolved ARPES spectroscopy: An ab initio approach, Phys. Rev. Materials 5, 083803, (2021).
