## EliashMEM
## What is it?
EliashMEM is a
program to extract the Eliashberg function directly from the
photoemission data. Basically, it takes input from the high resolution
photoemission measurement, and unfolds the Eliashberg function for the
electron-phonon (or other bosonic modes) coupling by fitting to the
quasi-particle dispersion. The Maximum Entropy Method (MEM) is employed
to overcome the numerical instability for a direct inversion.
¡@ This work is a collaborative effort involving researchers from a number of institutions: Junren Shi (Oak Ridge National Lab), S.-J. Tang (University of Tennessee), Biao Wu (University of Texas at Austin and ORNL), P.T. Sprunger (Louisiana State University), W. L. Yang, V. Brouet (Stanford University and Advanced Light Source of LNBL), X. J. Zhou (Stanford University), Z. Hussain (Advanced Light Source), Z.-X. Shen (Stanford University), Zhenyu Zhang and E. W. Plummer (University of Tennessee and ORNL). The details of the technique can be found in Phys. Rev. Lett. 92, 186401 (2004).
These slides
provide an overview to the technique.The related paper: "Identification of Multiple Fine Structures in Electron Self-Energy of La _{2-x}Sr_{x}CuO_{4},''
X. J. Zhou, Junren Shi, T. Yoshida, T. Cuk, W.L. Yang, V. Brouet,
J. Nakamura, N. Mannella, S. Komiya, Y. Ando, F. Zhou, W. X. Ti, J. W.
Xiong, Z. X. Zhao, T. Sasagawa, T. Kakeshita, H. Eisaki, S. Uchida, A.
Fujimori, Zhenyu Zhang, E. W. Plummer, R. B. Laughlin, Z. Hussain, and
Z.-X. Shen, submitted to Phys. Rev. Lett.¡@ ## InstallationThe source can
be downloaded here.
tar xvzf MEM.tgz
then edit Makefile to accommodate the settings of your system, and type
make
to build.
The executable is called
MEM3.
The examples directory includes a sample data set (dispersion.txt), which happens to be the data presented in the PRL paper, and the corresponding configuration file (CONF3.INI). To analysis the data, run the command in the examples directory: ¡@
../MEM3
¡@ ## Usage
## Input:The
program reads two input files. First is the dispersion data file from
the experimental measurement. It is in simple text format with two
columns: first column is the initial state energy in the unit of eV; the
second column is the momentum in arbitrary unit. Note that the program
only utilizes the data with energy below the Fermi energy.
## Output## The screen output:- ND: the number of data points utilized in the MEM fitting
- SIGMABAR: the average error bar of the real part of self-energy
- CHI^2: the
mean deviation of the final fitting: £q
^{2} - ALPHA: final value of a.
- LAMBDA: the
mass enhancement factor calculated
¡@ - DLAMBDA: error bar of the determined mass enhancement factor
- OMEGALOG: the average phonon frequency that appears in Eliashberg's Tc formula.
## Output Files:All output files
start with [Output Prefix] that is supplied in CONF3.INI file: - [Output Prefix].LOG: includes various information for the fitting.
- [Output Prefix]_SPT.dat: the Eliashberg function: column 1: £s (meV); 2: Eliashberg function; 3: constraint function
- [Output Prefix]_DAT.dat: Self energy data and fitting. column 1: initial state energy (meV); 2: real part of self energy data (meV); 3: error bars (meV); 4: fitting to the real part of self-energy (meV); 5: calculated imaginary part of self-energy (meV).
- [Output_Prefix]_DSP.dat:
Dispersion data and fitting: column 1: initial state energy data (eV);
2: momentum data; 3: fitting to the momentum data; 4: calculated
imaginary part of self-energy (eV); 5: calculated photoemission peak
width (FWHM).
¡@
## Working Flow
Unfortunately, the program is not fully automated. It still needs
inputs of human being to get proper settings of parameters. The most
important parameters are A0 and A1, which determine the bare particle
dispersion through £` ¡@ ## Issues and CommentsPlease
contact me (junrenshi@gmail.com) for questions, comments and
suggestions. ## LicenseThis
program is released in hopes that it will be useful for other
researchers. We can not be responsible for any consequence incurred by
this program, neither will we claim credit for the results obtained from
this program. ¡@ ¡@ |