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

Abstract

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 ͑2009͒ 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 ͑2004͒ with 25 nm layer separation at 0.07 K would produce a drag resistance ϳ10 −4 ⍀ according the vortex theory but only ϳ10 −12 ⍀ for the percolation theory. We provide details of our theoretical analysis of the drag resistance within both paradigms and report some results as well.

Coulomb drag

“…The theory of Coulomb drag between two 2DEGs was extended to dilute 2D hole systems (Hwang et al, 2003) and to the cases where one allows for certain tunneling processes between the layers (Oreg and Halperin, 1999;Oreg and Kamenev, 1998), interlayer disorder correlations (Gornyi et al, 1999;Hu, 2000a), in-plane potential modulation (Alkauskas et al, 2002), and disorder inhomogeneities (Apalkov and Raikh, 2005;Spivak and Kivelson, 2005;Zou et al, 2009Zou et al, , 2010. Theory of Coulomb drag between composite fermions was generalized to include phonon-mediated coupling (Bønsager et al, 2000;Khveshchenko, 2000).…”