Heavy-fermion metals with hybridization nodes: Unconventional Fermi liquids and competing phases

TL;DR

This paper investigates heavy-fermion metals with momentum-dependent hybridization, revealing how anisotropic hybridization influences thermodynamic, optical properties, and phase competition, with implications for experimental observations.

Contribution

It introduces models with momentum-dependent hybridization in heavy-fermion systems, highlighting the role of hybridization nodes in unconventional Fermi liquids and phase selection.

Findings

Anisotropic hybridization leads to heavy quasiparticles dominating low-temperature specific heat.

Unhybridized light electrons carry electrical conductivity at intermediate temperatures.

Momentum-space anisotropy influences the competition between Kondo screening and magnetic or superconducting phases.

Abstract

Microscopic models for heavy-fermion materials often assume a local, i.e., momentum-independent, hybridization between the conduction band and the local-moment f electrons. Motivated by recent experiments, we consider situations where this neglect of momentum dependence is inappropriate, namely when the hybridization function has nodes in momentum space. We explore the thermodynamic and optical properties of the highly anisotropic heavy Fermi liquid, resulting from Kondo screening in a higher angular-momentum channel. The dichotomy in momentum space has interesting consequences: While e.g. the low-temperature specific heat is dominated by heavy quasiparticles, the electrical conductivity at intermediate temperatures is carried by unhybridized light electrons. We then discuss aspects of the competition between Kondo effect and ordering phenomena induced by inter-moment exchange: We propose that the strong momentum-space anisotropy plays a vital role in selecting competing phases. Explicit results are obtained for the interplay of unconventional hybridization with unconventional, magnetically mediated, superconductivity, utilizing variants of large-N mean-field theory. We make connections to recent experiments on CeCoIn5 and other heavy-fermion materials.