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首页> 外文学位 >Electrical transport in indium oxide thin films near the magnetic field-induced superconductor-insulator transition.
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Electrical transport in indium oxide thin films near the magnetic field-induced superconductor-insulator transition.

机译：磁场诱导的超导体-绝缘体转变附近的氧化铟薄膜中的电传输。

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摘要

The effects of a perpendicular and a parallel magnetic field on amorphous indium oxide thin films near the superconductor-insulator transition have been investigated. The transport in insulating films exhibiting local superconductivity is found to be governed by three-dimensional Mott variable range hopping. At very low temperatures the application of relatively low perpendicular magnetic fields produces a giant positive magnetoresistance that increases with decreasing temperature. This suggests that the ground state in zero magnetic field is a Cooper pair insulator or a vortex superfluid. At nonzero temperatures a magnetic field induces this insulating behavior. The current-voltage characteristics at low temperatures which are nonlinear, exhibit temperature- and magnetic field-independent threshold voltages for enhanced conduction. This behavior suggests a connection with the presence of Cooper pairs and might be associated with the depinning of a charge structure. In superconducting films, the application of a relatively high magnetic field results in a non-superconducting state. The electrical transport in this non-superconducting regime of the thinner of two superconducting films follows two-dimensional Efros-Shklovskii variable range hopping, whereas that of the thicker one obeys a T 1/3 law characteristic of three-dimensional dirty metals. In contrast with what has been reported for amorphous indium oxide thin films with similar transition temperatures and critical fields, finite-size scaling analyses failed to produce a conclusive critical exponent product vz. This failure suggests that the phase transition in these films is to a normal metal with quantum corrections to their conductivity, rather than to an insulator. Structure and surface characterizations show that the films are amorphous, but have rough surfaces. This roughness may be responsible for the formation of regions with a high local density of Cooper pairs, which make the films effectively granular.
机译：研究了垂直磁场和平行磁场对超导体-绝缘体过渡附近的非晶氧化铟薄膜的影响。发现具有局部超导性的绝缘膜中的传输受三维Mott可变范围跳变控制。在非常低的温度下，施加相对较低的垂直磁场会产生巨大的正磁阻，该正磁阻会随着温度的降低而增加。这表明零磁场中的基态是库珀对绝缘子或涡旋超流体。在非零温度下，磁场会引起这种绝缘行为。低温下的电流-电压特性是非线性的，表现出与温度和磁场无关的阈值电压，以增强传导性。此行为表明与库珀对的存在有关，并且可能与电荷结构的固定相关。在超导膜中，施加相对较高的磁场会导致非超导状态。在两个超导薄膜的较薄层的这种非超导状态下，电传输遵循二维Efros-Shklovskii可变范围跳跃，而较厚的一个则遵循三维脏金属的T 1/3律特征。与报道的具有类似转变温度和临界场的非晶氧化铟薄膜相反，有限尺寸的定标分析未能得出结论性的临界指数产物vz。该失败表明这些膜中的相变是向其导电性进行了量子校正的普通金属，而不是绝缘体。结构和表面特征表明该膜是无定形的，但具有粗糙的表面。这种粗糙度可能导致形成具有高局部库珀对密度的区域，这使薄膜有效地形成颗粒。

著录项

  • 作者

    Tan, Kong Hauw Sarwa Bakti.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 117 p.
  • 总页数 117
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

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