Emergent Half Metal at Finite Temperatures in a Mott Insulator

TL;DR

This paper demonstrates that a Mott insulator can transition into a fully spin-polarized half-metal at finite temperatures through thermal fluctuations, offering a pathway to high-temperature spintronic applications.

Contribution

It reveals a mechanism where competing Mott and band insulator tendencies produce a finite-temperature half-metal via a first-order phase transition.

Findings

Thermal fluctuations induce a transition to a half-metal with 100% spin polarization.

Varying electron repulsion strength can increase the onset temperature of the half-metal.

The proposed mechanism can be realized experimentally in tunable materials.

Abstract

Sustaining exotic quantum mechanical phases at high temperatures is a long-standing goal of condensed matter physics. Among them, half-metals are spin-polarized conductors that are essential for realizing room-temperature spin current sources. However, typical half-metals are low-temperature phases whose spin polarization rapidly deteriorates with temperature increase. Here, we first show that a low-temperature insulator with an unequal charge gap for the two spin channels can arise from competing Mott and band insulating tendencies. We establish that thermal fluctuations can drive this insulator to a half-metal through a first-order phase transition by closing the charge gap for one spin channel. This half-metal has 100% spin polarization at the onset temperature of metallization. Further, varying the strength of electron repulsion can enhance the onset temperature while preserving spin polarization. We outline experimental scenarios for realizing this tunable finite temperature half-metal.