Anomalous Enhancement of Seebeck Coefficient in Pr-Based 1-2-20 System with Non-Kramers Doublet Ground States

International Conference on Strongly Correlated Electron Systems 2014

Machida, Y.^1 ; Yoshida, T.^1 ; Ikeura, T.^1 ; Izawa, K.^1 ; Nakama, A.^2 ; Higashinaka, R.^2 ; Aoki, Y.^2 ; Sato, H.^2 ; Sakai, A.^3 ; Nakatsuji, S.^3 ; Nagasawa, N.^4 ; Matsumoto, K.^4 ; Onimaru, T.^4 ; Takabatake, T.^4

Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo

152-8551, Japan^1

Department of Physics, Tokyo Metropolitan University, Tokyo, Hachioji

192-0397, Japan^2

Institute for the Solid State Physics, University of Tokyo, Chiba, Kashiwa

277-8581, Japan^3

Department of Quantum Matter, Hiroshima University, Higashi-Hiroshima, Hiroshima

739-8530, Japan^4

关键词: Conduction electrons;    Degree of freedom;    Heavy-fermion metals;    Low temperatures;    Mass enhancement;    Non-Kramers doublet;    Quadratic temperature;    Sommerfeld coefficient;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/592/1/012025/pdf
DOI  :  10.1088/1742-6596/592/1/012025

来源: IOP

【 摘 要 】

Low-temperature Seebeck coefficient S/T measurements have been performed on Pr-based 1-2-20 system, PrTr2X20(Tr Ti, Ta, V, Ir, X Al, Zn) with non-Kramers doublet ground states. For PrTr2X20with X Al, we find a large S/T, which amounts to those of heavy fermion metals. By contrast, S/T for PrIr2Zn20is found to be considerably small as the same order of magnitude as those of ordinary metals, despite the commonly enhanced Sommerfeld coefficient γ throughout the system. A satisfactory of the quasi-universal relation between S/T and γ as well as the Kadowaki-Woods relation demonstrates that the mass enhancement is realized in PrTr2Al20due to the hybridization between f-electrons and the conduction electrons. We also find that the small S/T of PrIr2Zn20is enhanced at low temperatures under the fields on the verge of quadrupole ordered phase, and in the same regime, the electrical resistivity follows the quadratic temperature dependence with a steep slope as a characteristic of Fermi liquid. The results imply an emergence of a nontrivial coherent state with sizable mass enhancement associated with the quadrupole degree of freedom.