Far-infrared plasma and electromagnetic waves in anisotropic superconductors

各向异性超导体中的远红外等离子体和电磁波

基本信息

批准号：
07455004
负责人：
UCHIDA Shin-ichi
金额：
$ 4.74万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

A plasma edge appearing in the c-axis polarized far-infrared reflectivity spectrum of high-T_C superconductors, which was first discovered for La-cuprates by our group, is now recognized as a general phenomenon of cuprate superconductors. For Bi cuprates the plasma frequency is located in the microwave region because of their extremely large anisotropy. This plasma is now called as Josephson plasma, since its appearance is connected to Josephson coupling between superconducting CuO_<> layrs.We have pursued, mainly on La_2-_XSr_XCuO_4 and YBa_<a2>Cu_3O_<7-y1>, how the Josephson plasma frequency varies with doping, Zn-substitution, and applied magnetic fields. In addition, using thin LSCO crystals, the propagation and dissipation of the plasma wave have been investigated. Major results and findings are :1.The Josephson plasma frequency (omega_p) is determined predominantly by the value of the c-axis normal-state resistivity just above T_c. The anisotropy of the high-T_c superconductors becomes weaker and thus the c-axis resistivity becomes lower as doping proceeds. It is demonstrated that the decrease in anisotropy leads to an increase in omega_p.2.It is shown that the high-T_c superconductors become transparent for c-axis polarized light with frequency higher than omega_p. This is explained by the propagation of a polariton which is a coupled electromagnetic wave between light and Josephson plasma. The polariton is found to suffur weak damping which arises from the gaplessness of high-T_c superconductivity, intrinsic of cooper pairing with d-wave symmetry.3.While omega_p in Bi cuprates is very sensitive to externally applied magnetic fields, that in La cuprates is found to be insensitive. This difference is ascribable to the difference in the vortex pinning strength, and it turns out that the pinning becomes stronger with increase of doping in any cuprate system.

高-T_C超导体的C轴极化远红外反射率谱显示的等离子体边缘最初是由我们的组为LA-I-Uprates发现的，现在被认为是Cuprate超导体的一般现象。对于Bi Cuprates，由于其极大的各向异性，血浆频率位于微波区域。现在，该等离子体被称为Josephson等离子体，因为它的外观与Josephson的耦合有关，主要是在LA_2-_XSR_XCUO_4和YBA___________________________3O_3O_3O_3O <7-y-y1>上，主要是在LA_2-_XSR_XCUO_4和YBA__XCCUO_4上进行的耦合，随掺杂，Zn-substitution和施加的磁场而变化。另外，使用薄的LSCO晶体，已经研究了血浆波的传播和耗散。主要结果和发现是：1。约瑟夫森等离子体频率（Omega_p）主要取决于T_C高于T_C的C轴正常状态电阻率的值。高-T_C超导体的各向异性变得较弱，因此随着兴奋剂的进行，C轴电阻率变得较低。证明各向异性的减少导致Omega_p.2的增加。证明高-T_C超导体对于C轴极化光的频率高于Omega_p的c轴偏振光变得透明。这是通过偏振子的传播来解释的，北极子是光和约瑟夫森等离子体之间的耦合电磁波。北极子被发现富含弱阻尼，这是由高-T_C超导性的无间隙引起的，库珀与d-wave对称性配对的固有性。3。bi cuprates中的omega_p对外部施加的磁场非常敏感，在la cuprates中是在la cuprates中是非常敏感的。发现不敏感。这种差异可归因于涡旋固定强度的差异，事实证明，随着任何丘比特系统中掺杂的增加，固定会变得更强大。