Single-Site Non-Fermi-Liquid Behaviors in a Diluted 4f2 System Y1−x

Abstract

Electrical resistivity ρ(T) and specific heat C(T) measurements have been made on the diluted 4f^{2} system Y(Pr)Ir_{2}Zn_{20}. Both data of ρ and magnetic specific heat C_{m} per Pr ion are well scaled as a function of T/T_{0}, where T_{0} is a characteristic temperature of non-Fermi-liquid (NFL) behaviors. Furthermore, the temperature dependences of ρ and C_{m}/T agree with the NFL behaviors predicted by the two-channel Kondo model for the strong coupling limit. Therefore, we infer that the observed NFL behaviors result from the single-site quadrupole Kondo effect due to the hybridization of the 4f^{2} states with multichannel conduction electrons.

Collapse of Ferroquadrupolar Order and Emergence of Non-Fermi Liquid Behavior in La1−xPrxTi2Al20

“…If C m /T divergently increases with −lnT on cooling far below the lowest temperature 0.37 K, manifestation of the single-site quadrupole Kondo effect is expected [8,15]. On the other hand, in some La-substituted Pr systems, C m /T approaches a constant value on cooling, which can be reproduced by a random two-level model due to possible atomic disorder [7,16]. To reveal the origin of the upturn of C m /T , further measurements of the specific heat and the electrical resistivity at the lower temperatures down to 0.1 K are needed.…”

“…Among them, PrIr 2 Zn 20 shows an antiferroquadrupole (AFQ) order at T Q = 0.11 K and a superconducting transition at T c = 0.05 K [5,6]. In addition, non-Fermi liquid behaviors were observed in a diluted Pr system Y 1−x Pr x Ir 2 Zn 20 for x ≤ 0.44; the magnetic specific heat divided by temperature follows C m /T ∝ −lnT and the differential electrical resistivity ∆ρ ∝ √ T [7]. The temperature variations agree with those predicted by the theoretical calculation based on the single-site quadrupole Kondo model [8].…”

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

“…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.…”

Development of Short-range Correlations of 4f Electrons in the Non-Kramers Γ3 System PrNb2Al20 at Low Temperatures Investigated by NMR Measurements

“…The Γ 3 ground state system having disorder often shows no phase transition and has large residual C/T at low temperatures. Such cases are regarded as a quadrupole glass state in analogy with a spin-glass state [6] or are interpreted by the random two-level model [7]. In both cases, the microscopic behavior of such state is still unclear.…”