Structure of the normal state and origin of the Schottky anomaly in the correlated heavy-fermion superconductor UTe₂

Abstract

The recently discovered UTe2 superconductor is regarded as a heavy-fermion mixed-valence system with very peculiar properties within the normal and superconducting (SC) states. It shows no signs of magnetic order, but has a strong anisotropy of magnetic susceptibility and SC critical field. In addition to a heavy-fermion-like behavior in the normal state, it exhibits a distinctive Schottky-type anomaly at ∼12 K and a characteristic excitations gap ∼35-40 K. Here, we show, by virtue of dynamical mean-field theory calculations with a quasiatomic treatment of electron correlations, that ab initio-derived crystal-field splitting of the 5f2 ionic configuration yields agreement with these experimental observations. A close analogy of the normal paramagnetic state of UTe2 to that of URu2Si2 in the Kondo arrest scenario is revealed. We consider the impact of anisotropic superexchange interactions within the U-U structural dimer on magnetization and development of strong orbital and magnetic moment fluctuations in UTe2.