Kondo Effect Due to Impurities with (5f)ⁿConfiguration: Fermi Liquid Versus Non-Fermi Liquid

Crystal Field Triplets: A New Route to Non-Fermi-Liquid Physics

“…The distortion lifts the triplet degeneracy, giving either a singlet or doublet ground state split by a value h Q , and destabilizes the novel triplet FP. Instead, we have two possible stable FP's: when the singlet lies lowest, a Fermi Liquid FP arises, and a ground doublet experiences a NFL FP, associated with the two-channel quadrupolar Kondo effect for tetragonal symmetry [4]. According to our NRG calculation, the crossover temperature below which the system flows away from the cubic FP to one of the above two varies as h 2 Q for a small distortion [17].…”

“…The possible ground states, which are accessed by varying the two parameters of the crystal field Hamiltonian, are Γ 3 , Γ 5 , or Γ 1 [16]. As argued elsewhere, the Γ 3 ground state will give rise to the two-channel quadrupolar Kondo effect upon coupling to conduction electrons [3,4,6]. The two-channels arise from coupling to a local quartet (Γ 8 ) of conduction electrons which may be described as a tensor product of states with two magnetic labels and two orbital (Γ 3 ) labels.…”

“…A number of theoretical scenarios have arisen to explain this non-Fermi lquid (NFL) physics, which broadly fall into two categories: (1) Localized, including models associated with peculiar symmetry allowed interactions between felectron moments and conduction electrons [2][3][4][5][6] or a disorder induced distribution of Kondo scales [7,8]. Among the first class of models, multi-channel Kondo Hamiltonians employing couplings between localized magnetic or orbital doublets (induced by crystalline electric field [CEF] splittings) and conduction electrons have been extensively studied [3][4][5][6]. (2) Extended, in which the NFL behavior is driven by coupling of electrons to lowlying modes induced by intersite f -moment interactions in proximity to a quantum critical point [9,10].…”

Pressure-Induced Non Fermi Liquid Behavior near a Magnetic Instability.

“…It is well known that the strength of hybridization is increased by an application of pressure. Recently the effect of hybridization on the stability of FL and/or NFL has been investigated by Koga and Shiba using Anderson model [30,31]. They calculated the phase diagram of the stability region of FL and NFL as a function of Coulomb U and Hund couplings JH.…”

“…Thus the present result is explained qualitatively by taking into account of their result. 4 Recently there have been several theoretical works about the instability of NFL and/or FL states [30][31][32][33] under the influence of external perturbation. The present results are planning to analyze in more detail on the light of these theoretical models.…”