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Scaling analysis of field-induced superconductor-insulator transition in two-dimensional tantalum thin films

The superconductor-insulator (SI) transition in two-dimensional Ta thin films is investigated by controlling both film thickness and magnetic field. An intriguing metallic phase intervening superconductor and an insulator phase is observed within a narrow range of film thickness and magnetic field. Finite scaling analysis has been performed to investigate the nature of the SI transition in the thickness-tuned metallic and superconducting samples. The critical exponents in the disorder-induced metallic samples are clearly different from the exponents obtained in the superconducting samples. Dynamical exponent z of the superconducting samples is consistent with the theoretical predictions (z = 1), while the exponent for the metallic samples is approximately 0.7. The discrepancy in the transition behaviors supports that the disorder induced metallic phase cannot be classified to the same universality class of the superconducting Ta thin films.