High temperature singlet-based magnetism from Hund's rule correlations

TL;DR

This paper demonstrates that USb2 is a high-temperature singlet ground state magnet driven by Hund's rule correlations, exhibiting unique electronic symmetry changes and magnetic phenomena.

Contribution

It provides the first experimental and theoretical evidence of a high-temperature singlet ground state magnet influenced by Hund's rule correlations.

Findings

USb2 enables strong Hund's rule alignment of local magnetic moments.

USb2 exhibits changes in atomic multiplet symmetry across magnetic transition.

USb2 may be understood as a high-temperature realization of a singlet ground state magnet.

Abstract

Uranium compounds can manifest a wide range of fascinating many-body phenomena, and are often thought to be poised at a crossover between localized and itinerant regimes for 5f electrons. The antiferromagnetic dipnictide USb2 has been of recent interest due to the discovery of rich proximate phase diagrams and unusual quantum coherence phenomena. Here, linear-dichroic X-ray absorption and elastic neutron scattering are used to characterize electronic symmetries on uranium in USb2 and isostructural UBi2. Of these two materials, only USb2 is found to enable strong Hund's rule alignment of local magnetic degrees of freedom, and to undergo distinctive changes in local atomic multiplet symmetry across the magnetic phase transition. Theoretical analysis reveals that these and other anomalous properties of the material may be understood by attributing it as the first known high temperature realization of a singlet ground state magnet, in which magnetism occurs through a process that resembles exciton condensation.