Search for New Quantum Effects in Superconducting Vortices

寻找超导涡旋中的新量子效应

基本信息

批准号：
12450003
负责人：
HANAGURI Tetsuo
金额：
$ 4.93万
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：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

In this study, we examined the electronic states of vortex states of various clean superconductors such as high-T_c cuprates, NbSe_2 and YNi_2B_2C by utilizing the surface impedance measurements, specific heat measurements and scanning tunneling microscopy (STM).We succeeded in building a surface impedance measurement apparatus which works at very low temperatures down to 0.5K under magnetic fields. By using this apparatus, we measured flux flow resistivity of YBa_2Cu_3O_y and strongly anisotropic s-wave superconductor YNi_2B_2C. From the analysis, we found that the electronic state of vortex core of YBa_2Cu_3O_y is in the so-called "moderately clean" regime and vortex core is somewhat different from classical normal state core. In YNi_2B_2C, flux flow resistivity was almost twice as large as that expected from the conventional Bardeen Stephen model. This result indicates that the energy dissipation in the vortex core is strongly affected by the anisotropy of the superconducting gap.We also measured the magnetic field H dependence of electronic specific heat coefficients of various NbSe_2 crystals and found that the quasi-particle density of states (QPDOS) deviates from conventional H-linear behavior with increasing sample purity. From measurements on the sample containing columnar defects introduced by heavy ion irradiation, we found that the QPDOS anomaly is brought by quasi particles outside of vortex cores. From the comparative resistivity measurements and STM observations, we conclude that the QPDOS anomaly is strongly correlated with the evolution of charge-density wave which coexists with superconductivity.

在这项研究中，我们通过利用表面阻抗测量值，特定的热量测量和扫描隧道显微镜（STM）来检查各种干净的超导体的涡流状态，例如高-T_C Cuprates，NBSE_2和YNI_2B_2C。通过使用此设备，我们测量了YBA_2CU_3O_Y的通量流电阻，并且强烈的各向异性S波超导体YNI_2B_2C。从分析中，我们发现YBA_2CU_3O_Y的涡旋核心的电子状态在所谓的“中等清洁”制度中，而涡流核心与经典的正常状态核心有所不同。在YNI_2B_2C中，通量流电阻率几乎是常规Bardeen Stephen模型预期的两倍。该结果表明，涡流中的能量耗散受到超导间隙的各向异性的强烈影响。我们还测量了各种NBSE_2晶体的电子特异性热系数的磁场h依赖性，并发现与常规h-lineal purolity的态度（qpdos）的准晶状体密度（qpdos）偏离了态度（qpdos）。从重离子照射引入的柱状缺陷的样品上的测量值中，我们发现QPDOS异常是由涡流核心外的准颗粒带来的。从比较电阻率测量和STM观测值中，我们得出结论，QPDOS异常与电荷密度波的演变密切相关，电荷密度波的演变与超导性并存。