A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, 630090, Russia.
Department of Physics, Novosibirsk State University, Novosibirsk, 630090, Russia.
Sci Rep. 2017 May 11;7(1):1718. doi: 10.1038/s41598-017-01753-w.
A reentrant temperature dependence of the normal state resistance often referred to as the N-shaped temperature dependence, is omnipresent in disordered superconductors - ranging from high-temperature cuprates to ultrathin superconducting films - that experience superconductor-to-insulator transition. Yet, despite the ubiquity of this phenomenon its origin still remains a subject of debate. Here we investigate strongly disordered superconducting TiN films and demonstrate universality of the reentrant behavior. We offer a quantitative description of the N-shaped resistance curve. We show that upon cooling down the resistance first decreases linearly with temperature and then passes through the minimum that marks the 3D-2D crossover in the system. In the 2D temperature range the resistance first grows with decreasing temperature due to quantum contributions and eventually drops to zero as the system falls into a superconducting state. Our findings demonstrate the prime importance of disorder in dimensional crossover effects.
在经历超导-绝缘相变的无序超导体中，普遍存在一种被称为“N 型温度依赖性”的正常态电阻的反向温度依赖性，其范围涵盖高温铜酸盐到超薄超导薄膜。然而，尽管这种现象无处不在，但它的起源仍然是一个争论的话题。在这里，我们研究了强无序超导 TiN 薄膜，并证明了反向行为的普遍性。我们提供了对 N 型电阻曲线的定量描述。我们表明，随着冷却，电阻首先随温度线性下降，然后通过标记系统中 3D-2D 交叉的最小值。在 2D 温度范围内，由于量子贡献，电阻最初随温度降低而增大，最终当系统落入超导状态时，电阻降至零。我们的发现表明了无序在维度交叉效应中的重要性。
