Hyperactivated resistance in TiN films on the insulating side of the disorder-driven superconductor-insulator transition
T. I. Baturina, A. Yu. Mironov, V. M. Vinokur∇, M. R. Baklanov+, C. Strunk*
Institute of Semiconductor Physics, 630090 Novosibirsk, Russia
∇Material Science Division, Argonne National Laboratory, Argonne, Ill. 60439 USA
+IMEC, B-3001 Leuven, Belgium
*Institut für experimentelle und angewandte Physik, Universität Regensburg, D-93025 Regensburg, Germany
PACS: 72.15.Rn, 73.50.-h, 74.40.+k, 74.78.-w
Abstract
We investigate the insulating phase that forms in a titanium
nitride film in a close vicinity of the disorder-driven
superconductor-insulator transition. In zero magnetic field the temperature
dependence of the resistance reveals a sequence of distinct regimes upon
decreasing temperature crossing over from logarithmic to activated behavior
with the variable-range hopping squeezing in between. In perpendicular
magnetic fields below 2 T, the thermally activated regime retains at
intermediate temperatures, whereas at ultralow temperatures, the resistance
increases faster than that of the thermally activated type. This indicates a
change of the mechanism of the conductivity. We find that at higher magnetic
fields the thermally activated behavior disappears and the magnetoresistive
isotherms saturate towards the value close to quantum resistance h/e2.