Electronic structure and anomalous band-edge absorption feature in multiferroic MnWO4: An optical spectroscopic study

TL;DR

This study explores the electronic structure and lattice dynamics of multiferroic MnWO4 using optical spectroscopy, revealing how spin configurations influence band-edge absorption and highlighting the role of spin-orbit coupling.

Contribution

It provides detailed optical spectroscopic analysis of MnWO4, identifying inter-band transitions, phonon modes, and the impact of magnetic fields on absorption features, emphasizing spin-orbit coupling effects.

Findings

Inter-band transitions identified above 2.5 eV

All infrared transverse optical phonon modes observed

Band-edge absorption around 2.2 eV varies with spin configuration

Abstract

We investigated the electronic structure and lattice dynamics of multiferroic MnWO4 by optical spectroscopy. With variation of polarization, temperature, and magnetic field, we obtained optical responses over a wide range of photon energies. The electronic structure of MnWO4 near to the Fermi level was examined, with inter-band transitions identified in optical conductivity spectra above a band-gap of 2.5 eV. As for the lattice dynamics, we identified all the infrared transverse optical phonon modes available according to the group-theory analysis. Although we did not observe much change in global electronic structure across the phase transition temperatures, an optical absorption at around 2.2 eV showed an evident change depending upon the spin configuration and magnetic field. The behavior of this band-edge absorption indicates that spin-orbit coupling plays an important role in multiferroic MnWO4.