Large Magnetoresistance and Spin-Polarized Heavy-Mass Electron State in a Doped Valence Bond Solid (Ti1-xVx)2O3

TL;DR

This study reveals a doped valence bond solid (Ti1-xVx)2O3 hosts a heavy-mass, spin-polarized electron state with large negative magnetoresistance, driven by polaron formation and lattice fluctuations, indicating strong electron correlations.

Contribution

It demonstrates the realization of a heavy-mass, spin-polarized electron state in a doped valence bond solid, highlighting the role of polaron formation and lattice dynamics in mass enhancement.

Findings

Observation of large negative magnetoresistance.

Effective mass of carriers is 1-2 orders larger than in typical doped semiconductors.

Doping dependence suggests electron-phonon interactions driven by lattice fluctuations.

Abstract

A heavy-mass electron state is realized in a doped valence bond solid (Ti1-xVx)2O3. In this system, itinerant holes mediate the mainly ferromagnetic RKKY interaction between the localized magnetic moments and become readily spin-polarized under a magnetic field, while showing large negative magnetoresistance. In spite of the ferromagnetic interaction among the carriers, their effective mass is found to be 1 or 2 orders of magnitude larger than that of usual doped semiconductors. Such strong mass renormalization is ascribable to the polaron formation on the Ti-dimer, where the spin-singlet state is originally formed. Doping dependence of the electronic specific-heat coefficient implies that the dimeric lattice fluctuation or softening is responsible for the enhanced electron-phonon interaction.