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Evidence for a finite temperature insulator


  I. Tamir [1]  ,  D. Kalok [1]  ,  M. Ovadia [1,2]  ,  S. Mitra [1]   ,  B. Sacepe [1,3,4]  ,  D. Shahar [1]  
 [1] Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 76100, Israel
[2] Present Address: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States.
[3] Univ. Grenoble Alpes, Institut NEEL, F-38042 Grenoble, France.
[4] CNRS, Institut NEEL, F-38042 Grenoble, France.

In superconductors the zero-resistance current-flow is protected from dissipation at finite temperatures (T) by virtue of the short-circuit condition maintained by the electrons that remain in the condensed state.

The recently suggested finite-T insulator and the “superinsulating" phase are different because any residual mechanism of conduction will eventually become dominant as the finite-T insulator sets-in. 

If the residual conduction is small it may be possible to observe the transition to these intriguing states. We show that the conductivity of the high magnetic field insulator terminating superconductivity in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero conductance at T < 0.04 K. We discuss our results in the light of theories that lead to a finite-T insulator.