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.

我们已经测量了与常规S波超导体相反的Yni_2b_2c.1中的低温热容量C_P和微波表面阻抗Z_S，C_P显示出几乎H^<0.5>依赖性。即使引入了柱状缺陷，这种H^<0.5>依赖性仍然存在，这些缺陷在圆柱缺陷引入后，这些缺陷会极大地且强烈干扰常规的涡旋晶格。另一方面，从Z_S获得的通量流电阻率几乎与H成正比，排除了涡流核心的缩小场景。综上所述，这些结果表明，YNI_2B_2C的涡流状态与常规的S-Wave对应物根本不同，因为在涡流核心周围的Dellocalized Quasiparticle状态与D-D-Wave Superoxuctors相似。自旋三旋转超导体SR_2RUO_4的超导间隙结构已根据热流的相对方向，晶体轴和2D RUO_2平面内旋转的磁场来测量平面内电导率。热导率的平面内变化与任何模型垂直于2D平面的线节点不兼容，并表明存在水平淋巴结。这些结果对试图解释三胞胎超导性机理的模型施加了强烈的限制。

项目成果

M.B.Gaifullin et al.: "Abrupt Change of Josephson Plasma Frequency…"Physical Review Letters. 84. 2945-2948 (2000)

M.B.Gaifullin 等人：“约瑟夫森等离子体频率的突然变化……”物理评论快报 84. 2945-2948 (2000)。

K.Izawa et al.: "Superconducting Gap Structure of Spin-Triplet…"Physical Review Letters, in press. (2001)

K. Izawa 等人：“自旋三重态的超导带隙结构……”物理评论快报，出版中（2001 年）。

K.Izawa, A.Shibata, H.Takahashi, Y.Matsuda, M.Hasegawa, N.Chikumoto, C.J.van der Beek, and M.Konczykowski: "Flux Flow Resistance and Transmittivity in Overdoped Tl_2Ba_2CuO_<6+δ>"J.Low Temp.Phys.. 117. 1193-1198 (1999)

K.Izawa、A.Shibata、H.Takahashi、Y.Matsuda、M.Hasekawa、N.Chikumoto、C.J.van der Beek 和 M.Konczykowski：“过掺杂 Tl_2Ba_2CuO_<6+δ> 中的磁通流阻和透射率”J .低温物理.. 117. 1193-1198 (1999)

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