Raman evidence for Orbiton-Mediated Multiphonon Scattering in Multiferroic TbMnO$_3$

TL;DR

This study uses temperature-dependent Raman spectroscopy to reveal orbiton-phonon interactions and spin-phonon coupling in multiferroic TbMnO₃, highlighting complex quasiparticle dynamics in this material.

Contribution

It provides experimental evidence for orbiton-mediated multiphonon scattering and spin-phonon coupling in TbMnO₃ through detailed Raman analysis.

Findings

High frequency Raman mode has a nearly constant intensity ratio (~0.6) across temperatures.

Anomalous softening of a phonon mode below T_N (~46 K) indicates strong spin-phonon coupling.

Observation of orbiton-phonon mixed nature in high frequency Raman modes.

Abstract

Temperature-dependent Raman spectra of TbMnO$_3$ from 5 K to 300 K in the spectral range of 200 to 1525 cm$^{-1}$ show five first-order Raman allowed modes and two high frequency modes. The intensity ratio of the high frequency Raman band to the corresponding first order Raman mode is nearly constant and high ($\sim$ 0.6) at all temperatures, suggesting a orbiton-phonon mixed nature of the high frequency mode. One of the first order phonon modes shows anomalous softening below T$_N$ ($\sim$ 46 K), suggesting a strong spin-phonon coupling.