RIXS EPC Analysis (SrTiO3 and KTaO3)

This repository contains MATLAB code for the analysis of resonant inelastic x-ray scattering (RIXS) spectra to extract mode-resolved electron–phonon coupling (EPC) in SrTiO3 and KTaO3.

The implementation is based on multi-phonon modeling of RIXS spectra using externally determined phonon energies.

This work was carried out at the Laboratory for Quantum Matter Research (LQMR), University of Zurich, under the supervision of Prof. Dr. Johan Chang.

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Overview

The workflow consists of:

1. Visualization of raw RIXS spectra
2. Multi-phonon fitting of spectra
3. Extraction of coupling constants (g) and EPC strengths (M)
4. Convergence testing of intermediate-state cutoffs
5. Calibration of the elastic line using carbon tape

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Repository Structure

• main.m
  Main analysis script. Performs multi-phonon fitting and extracts EPC parameters.
  See: main.md

• raw_spectra.m
  Generates plots of raw RIXS spectra.
  See: raw_spectra_README.md

• convergence_test.m
  Tests convergence of intermediate-state cutoffs.
  See: convergence_test_README.md

• carbon_tape_fit.m
  Determines experimental resolution via elastic peak fitting.
  See: carbon_tape_fit_README.md

• functions/
  Contains material-specific multi-phonon fitting functions. These are the original base functions provided by Dr. Leonardo Martinelli and Severin Fluckiger.

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Data

Experimental HDF5 data are not included.

To run the analysis, data must be placed in:

hdf5_data/

Access to the data can be requested from the original authors (Dr. Leonardo Martinelli).

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Usage

Run main analysis:

main

Plot raw spectra:

raw_spectra

Run convergence tests:

convergence_test

Run carbon tape tests:

carbon_tape_fit

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Associated Thesis

This repository accompanies the Master's thesis:

"Quantifying Electron-Phonon Coupling in SrTiO₃ and KTaO₃ via Infrared and Resonant Light Spectroscopy"
University of Zurich, 2026

The thesis provides the full theoretical background, implementation details, and analysis methodology used in this codebase.

A copy is included in:

thesis/

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Acknowledgements

These functions are based on original implementations developed by Dr. Leonardo Martinelli and Severin Flückiger.

The present version extends these methods for the analysis of RIXS data and the extraction of electron–phonon coupling parameters.