Electronic state of vortices in YBa 2 Cu 3 O y investigated by complex surface impedance measurements
Electronic state of vortices in YBa 2 Cu 3 O y investigated by complex surface impedance measurements
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通过复表面阻抗测量研究 YBa 2 Cu 3 O y 中涡旋的电子态
DOI：
10.1103/physrevb.63.184517
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发表时间：
2001
影响因子：
3.7
通讯作者：
N. Kobayashi
中科院分区：
文献类型：
--
作者：
Y. Tsuchiya;K. Iwaya;K. Kinoshita;T. Hanaguri;H. Kitano;A. Maeda;K. Shibata;T. Nishizaki;N. Kobayashi
为了研究涡核内外的电子态，测量了${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$混合态对微波的电磁响应。低温下复合表面阻抗随磁场的变化规律与一般的涡旋动力学描述相吻合，假设涡旋上的粘性阻尼力和线性恢复力是场无关的。换言之，复电阻率的实部和虚部在B中都是线性的，这是由d波超导体理论解释的。利用基于Coffey-Clem描述的复杂穿透深度的分析，我们估计在10K时的涡粘性为$(4\char21{}5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}{\mathrm{N}\mathrm{s}/\mathrm{m}}^{2}.$，该值对应于${\ensuremath{\omega}}_{0}\ensuremath{\tau}\ensuremath{\sim}0.3\char21{}0.5，其中，${\ensureath{\omega}}_{0}$和\ensureath{\tau}分别是涡核中的最小能隙频率和准粒子寿命。这些结果表明，YBCO中的涡核不是处于深度超清洁区域，而是处于中等清洁区域。高温超导体中中等清洁的涡核的研究具有重要意义，因为由于d波特性和铜酸盐超导体的量子性质，物理上可能会产生新的效应。还研究了旋涡晶格的一级相变过程中，{Z}{S}作为B的函数的行为。与${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{y}$(BSCCO)不同的是，YBCO的FOT周围没有观察到明显的异常。我们的结果表明，只有在像BSCCO这样的高度各向异性的二维涡系统中，才能观察到由于FOT处超流体密度的变化而导致的{X}{S}$的快速增加。我们从两种材料的层间耦合和能量尺度的不同来讨论这些结果。
The electromagnetic response to microwaves in the mixed state of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ (YBCO) was measured in order to investigate the electronic state inside and outside the vortex core. The magnetic-field dependence of the complex surface impedance at low temperatures was in good agreement with a general vortex dynamics description assuming that the field-independent viscous damping force and the linear restoring force were acting on the vortices. In other words, both real and imaginary parts of the complex resistivity, ${\ensuremath{\rho}}_{1},$ and ${\ensuremath{\rho}}_{2},$ were linear in B. This is explained by theories for d-wave superconductors. Using analysis based on the Coffey-Clem description of the complex penetration depth, we estimated that the vortex viscosity \ensuremath{\eta} at 10 K was $(4\char21{}5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}{\mathrm{N}\mathrm{s}/\mathrm{m}}^{2}.$ This value corresponds to ${\ensuremath{\omega}}_{0}\ensuremath{\tau}\ensuremath{\sim}0.3\char21{}0.5,$ where ${\ensuremath{\omega}}_{0}$ and \ensuremath{\tau} are the minimal gap frequency and the quasiparticle lifetime in the vortex core, respectively. These results suggest that the vortex core in YBCO is not in the deeply superclean regime but in the moderately clean regime. Investigation of the moderately clean vortex core in high-temperature superconductors is significant because physically new effects may be expected due to d-wave characteristics and to the quantum nature of cuprate superconductors. The behavior of ${Z}_{s}$ as a function of B across the first order transition (FOT) of the vortex lattice was also investigated. Unlike ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{y}$ (BSCCO), no distinct anomaly was observed around the FOT in YBCO. Our results suggest that the rapid increase of ${X}_{s}$ due to the change of superfluid density at the FOT would be observed only in highly anisotropic two-dimensional vortex systems like BSCCO. We discuss these results in terms of the difference of the interlayer coupling and the energy scale between the two materials.