CT-QMC with segment implementation: ALPS/CT-HYB-SEGMENT

ALPS/CT-HYB-SEGMENT solver implements the CT-HYB QMC algorithm and is developed by H. Hafermann, P. Werner, E. Gull. Only density-density interactions are taken into account.

A minimum working example is the following. Please be sure to turn on density_density option in model block (otherwise the simulation fails). We assumed that the executable is installed at “$HOME/opt/CT-HYB/bin/alps_cthyb”. The solver terminates after MAX_TIME (300 seconds in the following example) or the total number of SWEEPS has been reached.

[model]
density_density = True
[impurity_solver]
name = ALPS/cthyb-seg
exec_path{str} = $HOME/opt/CT-HYB/bin/alps_cthyb
MAX_TIME{int} = 300
cthyb.N_MEAS{int} = 50
cthyb.THERMALIZATION{int}=1000
cthyb.SWEEPS{int}=100000000
cthyb.TEXT_OUTPUT{bool} = False

ALPS/CT-HYB-SEGMENT has many input parameters. A complete list of the parameters can be obtained by the help command

$HOME/opt/CT-HYB/bin/alps_cthyb --help

The following optional parameters may be useful:

[impurity_solver]
cthyb.MEASURE_nn{bool} = True   # static density-density correlation functions
cthyb.MEASURE_nnw{bool} = True  # density-density correlation functions in frequency domain
cthyb.MEASURE_nnt{bool} = True  # density-density correlation functions <n(0) n(t)>
cthyb.MEASURE_g2w{bool} = True  # measure two-particle Green's function in frequency space

Please also refer to the wiki page for some descriptions on parameters.

The DCore interface generates input files for ALPS/CT-HYB-SEGMENT into a working directory at work/imp_shell<ish>_ite<ite> (ish is the index of the shell and ite is the iteration). Then, ALPS/CT-HYB-SEGMENT is executed in the working directory, and numerical results are stored there. For example, the occupation number and the double occupancy are saved in the file ‘observables.dat’.