Superconducting phase transitions in disordered NbTiN films

Abstract

The suppression of superconductivity in disordered systems is a fundamental problem of condensed matter physics. Here we investigate the superconducting niobium-titanium-nitride (Nb_{1-x}Ti_{x}N) thin films grown by atomic layer deposition (ALD) where disorder is controlled by the slight tuning of the ALD process parameters. We observe the smooth crossover from the disorder-driven superconductor-normal metal transition (often reffered to as fermionic mechanism) to the case where bosonic mechanism dominates and increasing disorder leads to formation of metal with Cooper pairing. We show that, in moderately disordered films, the transition to zero-resistance state occurs in a full agreement with the conventional theories of superconducting fluctuations and Berezinskii-Kosterlitz-Thouless transition. However, the critically disordered films violate this accord showing low-temperature features possibly indicating the Bose metal phase. We show that it is the interrelation between film's sheet resistance in the maximum, R_{max}, of the resistive curve R(T) and R_q = h/4e^2 that distinguishes between these two behaviors. We reveal the characteristic features in magnetoresistance of the critically disordered films with R_{max} > R_q

arXiv comment8 pages, 3 figures

References in corpus (18)

• Nature of the Quantum Metal in a Two-Dimensional Crystalline Superconductor
• Localized Superconductivity in the Quantum-Critical Region of the Disorder-Driven Superconductor-Insulator Transition in TiN Thin Films
• The Elusive Bose Metal
• On the existence of a Bose Metal at T=0
• Strongly disordered TiN and NbTiN s-wave superconductors probed by microwave electrodynamics
• Broadening of the Beresinkii-Kosterlitz-Thouless superconducting transition by inhomogeneity and finite-size effects
• Evidence for a Finite Temperature Insulator
• Extreme Sensitivity of the Superconducting State in Thin Films
• Superconducting phase transitions in ultrathin TiN films
• Particle-hole symmetry reveals failed superconductivity in the metallic phase of two-dimensional superconducting films
• Evidence of Collective Charge Behavior in the Insulating State of Ultrathin Films of Superconducting Metals
• Robustness of the Berezinskii-Kosterlitz-Thouless Transition in Ultrathin NbN Films near the Superconductor-Insulator Transition
• Effective 2D thickness for the Berezinskii-Kosterlitz-Thouless-like transition in a highly underdoped La${}_{2-x}$Sr${}_x$CuO${}_4$
• Superconductor-insulator transitions: Phase diagram and magnetoresistance
• Berezinskii-Kosterlitz-Thouless transition in homogeneously disordered superconducting films
• Charge Berezinskii-Kosterlitz-Thouless transition in superconducting NbTiN films
• The role of Coulomb interaction in superconducting NbTiN thin films
• Excessive Noise as a Test for Many-Body Localization