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

Abstract

The newly discovered UTe2 superconductor is regarded as a heavy fermion mixed-valence system with very peculiar properties within the normal and superconducting states. It shows no signs of magnetic order but strong anisotropy of a magnetic susceptibility and a superconducting critical field. In addition to the heavy fermion-like behavior in the normal state, it exhibits also a distinctive Schottky-type anomaly at about 12 K and a characteristic excitations gap ~35-40 K. Here we show, by virtue of dynamical mean-field theory calculations with a quasi-atomic treatment of electron correlations, that ab-initio derived crystal-field splitting of the 5f2 ionic configuration yields an agreement with these experimental observations. We analyze the symmetry of magnetic and multipolar moment fluctuations that might lead to the superconducting pairing at low temperatures. A close analogy of the normal paramagnetic state of UTe2 to that of URu2Si2 in the Kondo arrest scenario is revealed.