Kondo lattices with inequivalent local moments: Competitive vs. co-operative Kondo screening

摘要

While standard heavy fermion metals feature a single spin-1/2 local momentper unit cell, more complicated systems with multiple distinct local momentshave been synthesized as well, with Ce_3Pd_20(Si,Ge)_6 being one example. Here,we discuss the physics of a Kondo lattice model with two local-momentsublattices, coupled with different Kondo couplings to conduction electrons.The phase diagram will be strongly modified from that of the standard Kondolattice if the characteristic screening temperatures of the distinct momentsare well separated. Therefore, we investigate the interplay between the twoKondo effects using a local self-energy approximation via slave bosons. We findthat the two Kondo effects can either compete or co-operate depending on theconduction-band filling. In the regime of competition, small differences in thetwo Kondo couplings can lead to huge differences in the respective Kondoscales, due to non-trivial many-body effects. We also study the low-temperatureproperties of the collective heavy Fermi-liquid state and propose a connectionto depleted Kondo lattice systems.