Hund's metallicity and orbital-selective Mott localization of CrO$_{2}$ in the paramagnetic state

TL;DR

This study uses advanced electronic structure calculations to reveal that paramagnetic CrO₂ is a Hund's metal with orbital-selective Mott behavior, evolving into a heavy-fermion state at lower temperatures.

Contribution

It demonstrates the orbital-selective Mott phase and heavy-fermion evolution in paramagnetic CrO₂ using combined density-functional and dynamical mean-field theory.

Findings

CrO₂ is a strongly-correlated Hund's metal with mixed-valent Cr ions.

At high temperatures, CrO₂ exhibits an orbital-selective Mott phase.

Lowering temperature leads to a Kondo-like heavy-fermion state.

Abstract

We present electronic structure calculations of a CrO$_{2}$ compound in the paramagnetic state within the computational scheme of density-functional theory combined with dynamical mean-field theory. We find that CrO$_{2}$ in the paramagnetic state is a strongly-correlated Hund's metal with mixed-valent Cr ions. At high temperatures, CrO$_{2}$ shows an orbital-selective Mott phase, in which the Cr $d_{xy}$ orbital is Mott-localized while the other Cr $t_{2g}$ $d$ orbitals remain itinerant. When the temperature is lowered, the orbital-selective Mott state is found to evolve into a Kondo-like heavy-fermion state with a small pseudo gap at the Fermi level if the system remains in the paramagnetic state.