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Orbital ordering in LaMnO3 investigated by resonance Raman spectroscopy
1Institut für Angewandte Physik, Universität Hamburg, Jungiusstrasse 9, D-20355 Hamburg, Germany.
Physical Review Letters
|April 20, 2004
Summary
Orbital ordering in LaMnO3 causes unique excitations. Resonance Raman scattering reveals phonon Raman cross-section behavior near the orbiton-excitation energy, matching theoretical predictions.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Spectroscopy
Background:
- Orbital ordering in materials like LaMnO3 leads to complex electronic and magnetic properties.
- Understanding the excitation spectrum is crucial for characterizing these materials.
- Raman scattering is a powerful technique for probing vibrational and electronic excitations.
Purpose of the Study:
- To investigate the unconventional excitation spectrum arising from orbital ordering in LaMnO3.
- To explore the relationship between photon energy, dielectric function, and Raman scattering response.
- To validate theoretical models describing electron-phonon coupling in this material.
Main Methods:
- Resonance Raman scattering experiments with incident photon energies ranging from 1.7 to 5.0 eV.
- Spectral ellipsometry to determine the dielectric function of LaMnO3.
- Theoretical calculations based on the Franck-Condon mechanism.
Main Results:
- Observed resonant behavior of the phonon Raman cross section when laser frequency approaches the orbiton-excitation energy (~2 eV).
- Spectral ellipsometry provided the dielectric function, aiding in the interpretation of resonant effects.
- Excellent agreement between experimental data and theoretical calculations for multiphonon Raman scattering.
Conclusions:
- The study confirms the influence of orbital ordering on the excitation spectrum of LaMnO3.
- The Franck-Condon mechanism effectively explains the observed resonant Raman scattering phenomena.
- This work provides a detailed understanding of electron-phonon coupling in orbitally ordered materials.
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