Magnetic-field-induced Anderson localization in orbital selective antiferromagnet BaMn$_2$Bi$_2$

TL;DR

This study reveals a magnetic-field-driven metal-insulator transition in BaMn$_2$Bi$_2$, caused by Anderson localization, with strong orbital-dependent correlations and distinct behaviors among different $3d$ bands.

Contribution

It demonstrates a magnetic-field-induced Anderson localization in a multiorbital antiferromagnet, highlighting the role of orbital-dependent correlations and spin interactions.

Findings

Metal-insulator transition driven by magnetic field in BaMn$_2$Bi$_2$

Coexistence of weakly and strongly correlated $3d$ bands

Weakly correlated $d_{xy}$ band exhibits Anderson localization

Abstract

We report a metal-insulator transition (MIT) in the half-filled multiorbital antiferromagnet (AF) BaMn$_2$Bi$_2$ that is tunable by a magnetic field perpendicular to the AF sublattices. Instead of an Anderson-Mott mechanism usually expected in strongly correlated systems, we find by scaling analyses that the MIT is driven by an Anderson localization. Electrical and thermoelectrical transport measurements in combination with electronic band calculations reveal a strong orbital-dependent correlation effect, where both weakly and strongly correlated $3d$-derived bands coexist with decoupled charge excitations. Weakly correlated holelike carriers in the $d_{xy}$-derived band dominate the transport properties and exhibit the Anderson localization, whereas other $3d$ bands show clear Mott-like behaviors with their spins ordered into AF sublattices. The tuning role played by the perpendicular magnetic field supports a strong spin-spin coupling between itinerant holelike carriers and the AF fluctuations, which is in sharp contrast to their weak charge coupling.