Nonequilibrium theory of tunneling into a localized state in a superconductor
Nonequilibrium theory of tunneling into a localized state in a superconductor
复制标题
超导体局部态隧道效应的非平衡理论
DOI：
10.1103/physrevb.90.100508
复制
发表时间：
2013
影响因子：
3.7
通讯作者：
D. Mozyrsky
中科院分区：
文献类型：
--
作者：
I. Martin;D. Mozyrsky
全能隙超导体中的单一静态磁性杂质导致能隙内准粒子束缚态的形成。在远低于超导转变的温度下，状态的能量弛豫和自旋相移预计将受到指数抑制。这种状态的存在可以在电子隧道实验中检测为正偏压和负偏压下的一对电导峰。在这里，我们表明，对于任意弱的隧道强度，峰值必须相对于所施加的偏置对称。这与标准结果相反，标准结果是隧道电导与局部（通常是粒子空穴不对称）状态密度成正比。如果允许杂质态的有限密度，或者杂质耦合到另一个非超导平衡浴，则可以恢复不对称性。
A single static magnetic impurity in a fully-gapped superconductor leads to formation of an intragap quasiparticle bound state. At temperatures much below the superconducting transition, the energy relaxation and spin dephasing of the state are expected to be exponentially suppressed. The presence of such a state can be detected in electron tunneling experiments as a pair of conductance peaks at positive and negative biases. Here we show, that for an arbitrarily weak tunneling strength, the peaks have to be symmetric with respect to the applied bias. This is in contrast to the standard result that the tunneling conductance is proportional to the local (in general particle-hole asymmetric) density of states. The asymmetry can be recovered is one allows for either a finite density of impurity states, or that impurities are coupled to another, non-superconducting, equilibrium bath.