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Title: Nature of the Cooper-pair insulator beyond the transition
Plain: On the insulating side, some films such as amorphous indium oxide and titanium nitride show a giant resistance peak in a magnetic field and signs that electrons are still bound in pairs. How paired electrons form an insulator, and what sets its conduction, is open.
Precise: In amorphous InOx, TiN and nanopatterned Bi films on the insulating side of the field-tuned transition, $\rho \sim \operatorname{exp}(T_{0}/T)$ with $T_{0}$ peaking at a field $B_{\mathrm{peak}}$, the magnetoresistance peak spans several orders of magnitude, and patterned films show $h/2e$ periodic magnetoresistance (Stewart et al. 2007). Explain the pair-localization mechanism and $T_{0}(B)$, and determine whether abrupt current jumps in the $I-V$ curves reflect electron overheating (Altshuler, Kravtsov, Lerner and Aleiner 2009) or a distinct phase (proposed superinsulator).
Settled by: Electron-temperature measurement during nonlinear transport plus local probes of pair density in the insulator, compared with a theory of localized preformed pairs.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: (empty)