Quadrupole-driven non-Fermi-liquid and magnetic-field-induced heavy fermion states in a non-Kramers doublet system

Abstract

Orbital degrees of freedom in condensed matters could play important roles in forming a variety of exotic electronic states by interacting with conduction electrons. In 4f -electron systems, because of strong intra-atomic spin-orbit coupling, an orbitally degenerate state inherently carries quadrupolar degrees of freedom. The present work has focussed on a purely quadrupole-active system PrIr2Zn20 showing superconductivity in the presence of an antiferroquadrupole order at TQ = 0.11 K. We observed non-Fermi liquid (NFL) behaviors emerging in the electrical resistivity ρ and the 4f contribution to the specific heat, C 4f , in the paramagnetic state at T > TQ. Moreover, in magnetic fields B ≤ 6 T, all data set of ρ(T ) and C 4f (T ) are well scaled with characteristic temperatures T0's. This is the first observation of the NFL state in the nonmagnetic quadrupole-active system, whose origin is intrinsically different from that observed in the vicinity of the conventional quantum critical point. It implies possible formation of a quadrupole Kondo lattice resulting from hybridization between the quadrupoles and the conduction electrons with an energy scale of kBT0. At T ≤0.13 K, ρ(T ) and C 4f (T ) exhibit anomalies as B approaches 5 T. This is the manifestation of a field-induced crossover toward a Fermi-liquid ground state in the quadrupole Kondo lattice.PACS numbers:

Cubic hastatic order in the two-channel Kondo-Heisenberg model

“…Pressure enhances the superconductivity 46 , which is almost certainly unconventional. The in-field phase diagrams are even more interesting, as there is an intermediate heavy Fermi liquid region in all three materials, sandwiched between the zerofield order and a fully polarized high field state where all Kondo physics is lost 47,48 .…”

Effects of Magnetic Field on the Nonmagnetic Doublet Ground State in PrMgNi4

“…Details of the nuclear contribution will be published elsewhere. that the downward variation of ρ(T ) around the broad shoulder cannot be explained by formation of the quadrupole Kondo lattice [9,12] and the single-site quadrupole Kondo effect [14]. Moreover, as shown in the inset of Fig.…”

“…Recently, the coexistence of quadrupole order and superconductivity was observed in PrT 2 Zn 20 (T = Ir, Rh) and PrT 2 Al 20 (T = Ti, V), which suggests that the superconducting pair could be mediated by quadrupole fluctuations [8]. Furthermore, non-Fermi liquid (NFL) behaviors were observed not only in PrIr 2 Zn 20 [9] and PrRh 2 Zn 20 [10] but also in the diluted Pr system Y(Pr)Ir 2 Zn 20 [11,13], indicating a possible manifestation of the quadrupole Kondo effect [14]. As described above, the intensive works on the 4 f 2 systems have revealed a wide variety of phenomena due to the interactions between the multipolar degrees of freedom of the 4 f 2 electrons and conduction electrons.…”

Field-induced ferrohastatic phase in cubic non-Kramers doublet systems

“…These materials provide an ideal setting to resolve the role of the quadrupolar Kondo effect and explore hastatic order within a simpler setting. Several exhibit a dome of heavy Fermi liquid at finite magnetic fields 33,34 that is consistent with field-induced hastatic order.…”

“…Adding this H Q,M F to our FH mean-field Hamiltonian, we obtain the free energy and solve the saddle point equations, ∂F/∂λ = ∂F/∂µ = ∂F/∂b = ∂F/∂Q = 0; note that the AFQ mean-field is not justified within the SU (N ) large-N limit, and this mean-field theory is therefore not controlled. At zero and small fields, the Pr(Ir,Rh) 2 Zn 20 compounds order quadrupolarly, giving way to heavy Fermi liquid behavior at intermediate fields 33,34 . We qualitatively reproduce this behavior in our self-consistently calculated mean-field phase diagrams for FH and AFQ ansatze in magnetic field, shown in Fig.…”