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

Abstract

Microscopic models for heavy-fermion materials often assume a local, i.e., momentumindependent, 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 momentumspace 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.

Crystal-field and Kondo-scale investigations ofCeMIn5(M=Co, Ir, and Rh): A combined x-ray absorption and inelastic neutr

“…19 The importance of momentumdependent ͑q-dependent͒ hybridization in these and some semiconducting Kondo materials has been investigated by several groups. [20][21][22][23][24][25][26] Various groups attempted to determine the crystal-field scheme of these compounds, but there are significant discrepancies depending on the applied methods, which include bulk measurements based on transport, thermodynamic, and NMR experiments. 19,[27][28][29][30] Christianson et al 31,32 performed extensive inelastic neutron scattering ͑INS͒ studies but phonon contributions in the energy range of the magnetic scattering broadened crystal-field excitations due to hybridization effects and the enormous absorption of the sample's constituents make the determination of reliable magnetic intensities rather challenging.…”

Low Energy Scales of Kondo Lattices: Mean-field Perspective

“…Also, for the sake of clarity, the description was restricted to the 'standard' Kondo model. Of course, the mean-field approximation has been generalized and applied to more realistic models, with, for example, a momentumdependent hybridization between conduction electrons and f ions [51].…”

Tandem Pairing in Heavy-Fermion Superconductors

“…A simplified twodimensional model is sufficient to illustrate the basic physics, where the d-wave composite pair now comes from the combination of s-wave hybridization in channel one and d-wave hybridization in channel two [21,22]. The magnetism is included as an explicit RKKY interaction, J H between neighboring local moments hiji, generated by integrating out electron in bands far from the Fermi surface.…”