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
