Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films

TL;DR

This paper investigates the superconductor-insulator transition in ultrathin TiN films, revealing coexistence of phases and quantum fluctuation-driven transitions through resistance measurements under varying temperature and magnetic fields.

Contribution

It provides experimental evidence of a direct superconductor-insulator transition influenced by quantum phase fluctuations in two-dimensional TiN films.

Findings

Coexistence of superconducting and insulating phases.

Confirmation of a quantum phase fluctuation-driven SIT.

Observation of a metallic phase at high magnetic fields with resistance approaching h/e^2.

Abstract

Temperature- and magnetic-field dependent measurements of the resistance of ultrathin superconducting TiN films are presented. The analysis of the temperature dependence of the zero field resistance indicates an underlying insulating behavior, when the contribution of Aslamasov-Larkin fluctuations is taken into account. This demonstrates the possibility of coexistence of the superconducting and insulating phases and of a direct transition from the one to the other. The scaling behavior of magnetic field data is in accordance with a superconductor-insulator transition (SIT) driven by quantum phase fluctuations in two-dimensional superconductor. The temperature dependence of the isomagnetic resistance data on the high-field side of the SIT has been analyzed and the presence of an insulating phase was confirmed. A transition from the insulating to a metallic phase is found at high magnetic fields, where the zero-temperature asymptotic value of the resistance being equal to h/e^2.