Anomalous Temperature Dependence of Lower Critical Field in Ultraclean URu<sub>2</sub>Si<sub>2</sub>

DOI DOI Web Site 8 Citations 45 References Open Access
  • Ryuji Okazaki
    Department of Physics, Kyoto University, Kyoto 606-8502, Japan
  • Masaaki Shimozawa
    Department of Physics, Kyoto University, Kyoto 606-8502, Japan
  • Hiroaki Shishido
    Department of Physics, Kyoto University, Kyoto 606-8502, Japan
  • Marcin Konczykowski
    Laboratoire des Solides Irradiés, CNRS-UMR 7642 & CEA/DSM/DRECAM, Ecole Polytechnique, 91128, Palaiseau, France
  • Yoshinori Haga
    Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
  • Tatsuma D. Matsuda
    Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
  • Etsuji Yamamoto
    Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
  • Yoshichika Ōnuki
    Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
  • Yoichi Yanase
    Department of Physics, Niigata University, Niigata 950-2181, Japan
  • Takasada Shibauchi
    Department of Physics, Kyoto University, Kyoto 606-8502, Japan
  • Yuji Matsuda
    Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Description

To investigate a mysterious superconducting state of URu_2Si_2 embedded in the so-called hidden order state, the lower critical field H_{c1} is precisely determined down to 55 mK for H || a and H || c. For this purpose, the positional dependence of the local magnetic induction is measured on ultraclean single crystals (T_c = 1.4 K) with residual resistivity ratio exceeding 700. We find that the temperature dependence of H_{c1} significantly differs from that of any other superconductors. The whole H_{c1}(T) for H || a are well explained by the two superconducting gap structures with line and point nodes, which have been suggested by the recent thermal conductivity and specific heat measurements. On the other hand, for H || c, a change of slope with a distinct kink in H_{c1}(T), which cannot be accounted for by two gaps, is observed. This behavior for H || c sharply contrasts with the cusp behavior of H_{c1}(T) associated with a transition into another superconducting phase found in UPt_3 and U_{1-x}Th_xBe_{13}. The observed anomalous low-field diamagnetic response is possibly related to a peculiar vortex dynamics associated with chiral domains due to the multicomponent superconducting order parameter with broken time reversal symmetry.

7 pages, 4 figures; accepted in J. Phys. Soc. Jpn

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