Theoretical analysis of drag resistance in amorphous thin films exhibiting superconductor-insulator transitions

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 distinct measurement in Y. Zou, G. Refael, and J. Yoon, Phys. Rev. B 80, 180503 (2009) 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 G. Sambandamurthy, L. W. Engel, A. Johansson, and D. Shahar, Phys. Rev. Lett. 92, 107005 _2004_ with 25 nm layer separation at 0.07 K would produce a drag resistance ~10^(−4) Ω according the vortex theory but only ~10^(−12) Ω for the percolation theory. We provide details of our theoretical analysis of the drag resistance within both paradigms and report some results as well

Investigating superconductor-insulator transition in thin films using drag resistance:Theoretical analysis of a proposed experiment

The magnetically driven superconductor-insulator transition in amorphous thin films (e.g., InO, Ta) exhibits several mysterious phenomena, such as a putative metallic phase and a huge magnetoresistance peak. Unfortunately, several conflicting categories of theories, particularly quantum-vortex condensation, and normal region percolation, explain key observations equally well. We propose a new experimental setup, an amorphous thin-film bilayer, where a drag resistance measurement would clarify the role quantum vortices play in the transition, and hence decisively point to the correct picture. We provide a thorough analysis of the device, which shows that the vortex paradigm gives rise to a drag with an opposite sign and orders of magnitude larger than the drag measured if competing paradigms apply.Comment: 5 pages, 2 figure

Magnetically Induced Metallic Phase in Superconducting Tantalum Films

We have studied the electronic transport properties of homogeneously disordered superconducting tantalum thin films in magnetic fields. The films exhibit three distinct transport regimes in the zero temperature limit which we identify as superconducting, metallic, and insulating phases. The metallic phase is unexpected. The transport characteristics of this metallic phase are found to be similar to those of MoGe films and high mobility dilute two-dimensional electrons or holes confined in semiconductor interface or transistor geometry.Comment: four pages, four figure

A Study on the Role of Information Systems in Organizational Growth: A Longitudinal Case Study

The purpose of this paper is to present an integrated framework which can explain how the role of information systems evolves in organizations. To develop the framework, two critical dimensions, each of which is classified further into three categories, are selected to explain the role of information systems in organizational growth: the purpose of information processing, the scope of information processing. As these are considered to be major dimensions underpinning much research regarding the role of information systems in organizations, the framework proposed in this paper could serve to integrate much existing research, while stimulating future research aimed at verifying its applicability

Non-thermal origin of nonlinear transport across magnetically induced superconductor-metal-insulator transition

We have studied the effect of perpendicular magnetic fields and temperatures on the nonlinear electronic transport in amorphous Ta superconducting thin films. The films exhibit a magnetic field induced metallic behavior intervening the superconductor-insulator transition in the zero temperature limit. We show that the nonlinear transport in the superconducting and metallic phase is of non-thermal origin and accompanies an extraordinarily long voltage response time.Comment: 5 pages, 4 figure

Evidence of spatial inhomogeneity near the onset of magnetically induced insulating state in superconducting thin films

Non-monotonic differential resistance (dV/dI) is observed in magnetically induced insulating films which exhibit apparent superconductor-metal-insulator transitions in the low temperature limit; at low bias currents the nonlinear transport is insulator-like while at high bias currents it is characteristic of metallic phase. The non-monotonic dV/dI may be evidence that the insulating state consists of metallic domains connected by point contacts (insulating gaps), implying that spatial inhomogeneities play a dominant role in determining the nature of the apparent metal-insulator transition.Comment: 4 pages, 3 figure