超导体-绝缘体转变非晶薄膜阻力的理论分析
Theoretical Analysis of Drag Resistance in Amorphous Thin Films Exhibiting Superconductor-Insulator-Transition
摘要：
非晶薄膜中的磁场调谐超导体-绝缘体转变，例如，Ta和InO，表现出一系列尚未解释的奇怪现象，如一个假定的低电阻金属相介入超导和绝缘相，以及在大磁场下磁阻的巨大峰值。定性地说，这些现象可以在几个显著不同的图像中得到同样好的解释，特别是量子涡旋液体的凝聚，以及嵌入正常区域的超导岛的渗透。最近，我们提出并分析了一种新的测量，应该能够果断地指向正确的图片：在非晶薄膜双层设置的阻力测量。在忽略层间隧穿的情况下，我们发现涡旋模式中的阻力具有相反的符号，并且比竞争模式中的阻力大几个数量级。例如，如Sambandamurthy等人2004中的两个相同的膜，在0.07 K下具有25 nm的层间距，根据涡旋理论将产生拖曳阻力$\sim10^{-4}Ω$，但对于渗滤理论仅产生$\sim10^{-12}Ω$。我们提供的细节，我们的理论分析的阻力在这两种范式，并报告一些新的结果。
英文摘要：
The magnetical field tuned superconductor-insulator transition in amorphous thin films, e.g., Ta and InO, exhibits a range of yet unexplained curious phenomena, such as a putative low-resistance metallic phase intervening the superconducting and the insulating phase, and a huge peak in the magnetoresistance at large magnetic field. Qualitatively, the phenomena can be explained equally well within several significantly different pictures, particularly the condensation of quantum vortex liquid, and the percolation of superconducting islands embedded in normal region. Recently, we proposed and analyzed a new measurement that should be able to decisively point to the correct picture: a drag resistance measurement in an amorphous thin-film bilayer setup. Neglecting interlayer tunneling, we found that the drag resistance within the vortex paradigm has opposite sign and is orders of magnitude larger than that in competing paradigms. For example, two identical films as in Sambandamurthy et al. 2004 with 25 nm layer separation at 0.07 K would produce a drag resistance $\sim10^{-4}Ω$ according the vortex theory, but only $\sim10^{-12}Ω$ for the percolation theory. We provide details of our theoretical analysis of the drag resistance within both paradigms, and report some new results as well.
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