Optical study of phonons and electronic excitations in tetragonal Sr$_2$VO$_4$

TL;DR

This study investigates the optical properties of Sr$_2$VO$_4$, identifying phonon modes and electronic excitations, and discusses their evolution with temperature in relation to phase transitions and the material's unique spin-orbital ground state.

Contribution

It provides a detailed optical excitation spectrum of Sr$_2$VO$_4$, including phonon modes and electronic transitions, enhancing understanding of its complex spin-orbital interactions.

Findings

Identification of phonon modes and their temperature evolution.

Observation of two additional electronic excitations at 290 cm$^{-1}$ and 840 cm$^{-1}$.

Discussion of results in context of spin-orbital ground state studies.

Abstract

We report on the optical excitation spectra in Sr$_2$VO$_4$. The phonon modes are assigned and their evolution with temperature is discussed in the frame of the different phase transitions crossed upon cooling. Besides the expected infrared-active phonons we observe two additional excitations at about 290 cm$^{-1}$ and 840 cm$^{-1}$ which could correspond to electronic transitions of the V$^{4+}$ ions. Our experimental results are discussed in the context of recent experimental and theoretical studies of this material with a unique spin-orbital ground state.