Nodal gap structure of the heavy-fermion superconductor URu2Si2 revealed by field-angle-dependent specific-heat measurements

International Conference on Strongly Correlated Electron Systems 2016

Kittaka, Shunichiro^1 ; Shimizu, Yusei^1 ; Sakakibara, Toshiro^1 ; Haga, Yoshinori^2 ; Yamamoto, Etsuji^2 ; O'Nuki, Yoshichika^2,3 ; Tsutsumi, Yasumasa^4,5 ; Nomoto, Takuya^6 ; Ikeda, Hiroaki^7 ; Machida, Kazushige^7

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

277-8581, Japan^1

Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Tokai

319-1195, Japan^2

Department of Physics, University of the Ryukyus, Nishihara, Okinawa

903-0213, Japan^3

Department of Basic Science, University of Tokyo, Tokyo

153-8902, Japan^4

Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama

351-0198, Japan^5

Department of Physics, Kyoto University, Kyoto

606-8502, Japan^6

Department of Physics, Ritsumeikan University, Kusatsu, Shiga

525-8577, Japan^7

关键词: d-Wave superconductors;    Field-angle-dependent;    Gap structures;    High quality single crystals;    In-plane fields;    Lower temperatures;    Measurements of;    Quasiparticle excitations;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/807/5/052001/pdf
DOI  :  10.1088/1742-6596/807/5/052001

来源: IOP

【 摘 要 】

URu2Si2is a promising candidate for a chiral d-wave superconductor whose gap is composed of a horizontal line node at equator and point nodes at the north and south poles. However, previous measurements of the specific heat and the thermal conductivity did not detect quasiparticle excitations from a horizontal line node in heavy-mass bands. Here, we have provided strong evidence for the presence of a horizontal line node from field-angle-dependent specific-heat measurements by using a high-quality single crystal of URu2Si2. We observed the behavior of the specific heat at low fields which does not depend on inplane field angle φ but shows a shoulder-like anomaly in the polar-angle θ dependence around θ ∼ 45°. This feature is more clearly seen at lower temperatures, suggesting the detection of low-energy quasiparticle excitations reflecting the gap structure. From theoretical analyses based on microscopic calculations, we have demonstrated that this anomaly can be explained by the existence of a horizontal line node at kz= 0. Thus, the gap structure of URu2Si2matches well with the Egchiral kz(kx+ iky) symmetry.