Thermal transport of uncomventional superconductors at low temperatures

非常规超导体在低温下的热传输

• 批准号: 11640336
• 负责人: MATSUDA Yuji
• 金额: $ 2.3万
• 依托单位: Institute for Solid State Physics, Univ of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640336/
• 关键词: heat Capacity; Surface Impedance; Vortex State; Unconventional Superconturctor; YNi_2B_2C; Sr_2RuO_4; Thermal Conductivity; Flux Flow; 異方的超伝導体; 高温超伝導体; Ru酸化物; ボロンカーバイド

We have measured the low temperature heat capacity C_p and microwave surface impedance Z_s in the vortex state of YNi_2B_2C.In contrast to conventional s-wave superconductors, C_p shows a nearly H^<0.5>-dependence. This H^<0.5>-dependence persists even after the introduction of the columnar defects which change the electronic structure of the vortex core regime dramatically and strongly disturb the regular vortex lattice. On the other hand, flux flow resistivity obtained from Z_s is nearly proportional to H, ruling out the vortex core shrinking scenario. Taken together, these results indicate that the vortex state of YNi_2B_2C is fundamentally different from the conventional s-wave counterparts, in that the delocalized quasiparticle states around the vortex core play a much more important role, similar to d-wave superconductors.To clarify the superconducting gap structure of the spin-triplet superconductor Sr_2RuO_4, the in-plane thermal conductivity has been measured as a function of relative orientations of the thermal flow, the crystal axes, and a magnetic field rotating within the 2D RuO_2 planes. The in-plane variation of the thermal conductivity is incompatible with any model with line nodes vertical to the 2D planes and indicates the existence of horizontal nodes. These results place strong constraints on models that attempt to explain the mechanism of the triplet superconductivity.

我们测量了YNi_2B_2C涡旋状态下的低温热容C_p和微波表面阻抗Z_s。与传统的横波超导体相比，C_p表现出接近H^<0.5>的依赖性。即使在引入柱状缺陷之后，这种 H^<0.5> 依赖性仍然存在，柱状缺陷极大地改变了涡旋核心区域的电子结构并强烈干扰了规则涡旋晶格。另一方面，从 Z_s 获得的通量流电阻率几乎与 H 成正比，排除了涡核收缩的情况。综上所述，这些结果表明，YNi_2B_2C的涡旋态与传统的s波涡旋态有着根本的不同，涡旋核心周围的离域准粒子态起着更重要的作用，类似于d波超导体。为了阐明自旋三重态超导体Sr_2RuO_4的超导带隙结构，面内热 电导率被测量为热流相对方向、晶轴和二维 RuO_2 平面内旋转磁场的函数。热导率的面内变化与任何具有垂直于二维平面的线节点的模型都不兼容，并且表明水平节点的存在。这些结果对试图解释三重态超导机制的模型施加了很大的限制。

项目成果

M.B. Gaifullin, Y. Matsuda et al.: "C-axis superfluid response and quasiparticle"Phys. Rev. Lett.. 83. 3928-3931 (1999)

M.B.

M.Kusugi, Y.Matsuda, M.B.Gaifullin, L.N.Bulaevskii, N.Chikumoto, M.Konczykowski, J.Shimoyama, K.Kishio, K.Hirata, and K.Kumagai: "Josephson Coupling in the Vortex Liquid State of Bi_2Sr_2CaCu_2O_<8+δ> with Columnar Defects."Phys.Rev.B. 59. 8970-8977 (1999

M.Kusugi、Y.Matsuda、M.B.Gaifullin、L.N.Bulaevskii、N.Chikumoto、M.Konczykowski、J.Shimoyama、K.Kishio、K.Hirata 和 K.Kumagai：“Bi_2Sr_2CaCu_2O_ 涡流液态下的约瑟夫森耦合< 8+δ> 具有柱状缺陷。”Phys.Rev.B. 59. 8970-8977 (1999

M.B.Gaifullin, Yuji Matsuda, N.Chikumoto, J.Shimoyama, K.Kishio, and R.Yoshizaki: "c-Axis Superfluid Response and Quasiparticle Damping of Underdoped Bi : 2212 and Bi : 2201"Phys.Rev.Lett.. 83. 3928-3931 (1999)

M.B.Gaifullin、Yuji Matsuda、N.Chikumoto、J.Shimoyama、Kishio 和 R.Yoshizaki：“欠掺杂 Bi 的 c 轴超流体响应和准粒子阻尼：2212 和 Bi：2201”Phys.Rev.Lett.. 83

T.Shibauchi, Yuji Matsuda, M.B.Gaifullin, and T.Tamegai: "Comment on " Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductor κ- (BEDT-TTF)_2Cu(NCS)_2""Phys.Rev.Lett.. (in pre

T. Shibauchi、Yuji Matsuda、M.B. Gaifullin 和 T. Tamegai：“分子超导体 κ- (BEDT-TTF)_2Cu(NCS)_2 中超导有序参数各向异性的毫米波磁光测定”评论“”Phys.Rev.Lett..（预

K.Kumagai, K.Nozaki, and Y.Matsuda: "Charged Vortices in High Temperature Superconductors Probed by NMR."Phys.Rev.B. (in press). (2001)

K.Kumagai、K.Nozaki 和 Y.Matsuda：“通过 NMR 探测高温超导体中的带电涡流”Phys.Rev.B。