Quantum Fluctuations of the Order Parameter in Superconductors

该奖项支持研究低维超导体中量子涨落的理论研究和教育。计划了三个项目：(1)研究人员将计算对现有的超导薄膜上临界场平均场理论的修正。他们将考虑导致超导液滴出现在BCS上临界场以上的杂质分布的介观效应。超导液滴的约瑟夫森网络在低温下可能变成宏观超导。真正的相变点是由序参数的量子涨落和邻近效应的相互作用决定的。将考虑相变附近各种物理量的行为，并与现有的标度理论进行接触。(2)研究人员将建立一个关于约瑟夫森结的有限长导线和链的零温度超导转变的理论。这项工作的动机是实验表明，在低温下，热电阻率会出现偏差。(3)研究人员将计算铁磁-d波超导体结的I-V特性，包括自旋-轨道耦合的影响。图解展开和凯尔德什技术是将要使用的各种分析技术之一。该奖项支持低温下超导体量子力学涨落的理论研究和教育。研究人员将使用先进的理论方法来研究量子涨落在超导薄膜、超导线和涉及超导体的结中的作用。这项研究是基础性的，对我们理解其他系统中的量子相变具有潜在的影响。

This award supports theoretical research and education to study quantum fluctuations in low-dimensional superconductors. Three projects are planned: (1) The investigators will calculate corrections to the existing mean-field theory of the upper critical field in thin superconducting films. They will consider mesoscopic effects in the distribution of impurities that lead to the appearance of superconducting droplets above the BCS upper critical field. The Josephson network of the superconducting droplets may become macroscopically superconducting at low temperatures. The genuine transition point is determined by the interplay of the quantum fluctuations of the order parameter and the proximity effect. The behavior of various physical quantities near the transition will be considered and contact with the existing scaling theory will be made. (2) The investigators will construct a theory of the zero-temperature superconducting transition in finite-length wires and chains of Josephson junctions. This work is motivated by experiments that show deviations from a thermally activated resistivity at low temperatures. (3) The investigators will calculate I-V characteristics for a ferromagnet - d-wave superconductor junction including the effects of spin-orbit coupling. Diagrammatic expansions and the Keldysh technique are among the variety of analytical techniques that will be used. %%% This award supports theoretical research and education on quantum mechanical fluctuations in superconductors at low temperatures. The investigators will use advanced theoretical methods to study the role of quantum fluctuations in thin superconducting films, superconducting wires, and junctions involving superconductors. This research is fundamental and has potential impact on our understanding of quantum phase transitions in other systems.***