Reentrant Resistive Behavior and Dimensional Crossover in Disordered Superconducting TiN Films

Abstract

A reentrant temperature dependence of the normal state resistance often referred to as the N-shaped temperature dependence, is omnipresent in disordered superconductors – ranging from high-temperature cuprates to ultrathin superconducting films – that experience superconductor-to-insulator transition. Yet, despite the ubiquity of this phenomenon its origin still remains a subject of debate. Here we investigate strongly disordered superconducting TiN films and demonstrate universality of the reentrant behavior. We offer a quantitative description of the N-shaped resistance curve. We show that upon cooling down the resistance first decreases linearly with temperature and then passes through the minimum that marks the 3D–2D crossover in the system. In the 2D temperature range the resistance first grows with decreasing temperature due to quantum contributions and eventually drops to zero as the system falls into a superconducting state. Our findings demonstrate the prime importance of disorder in dimensional crossover effects.

Quantum superconductor-insulator transition in titanium monoxide thin films with a wide range of oxygen contents

“…Superconductor-insulator transition (SIT) as one fascinating example of quantum phase transitions [1] has remained an active topic in recent years. The SIT could be controlled by various non-thermal tuning parameters [2], including disorder [3][4][5][6], thickness [7][8][9], magnetic field [4,7,10,11], chemical composition [12,13], carrier density [4,14], and gate voltage [15,16] in two dimensional (2D) superconductors.…”

Superconductivity in a disordered metal with Coulomb interactions

“…We find τ 0 = 7.3 ± 0.3 × 10 −15 s. With this, we find R = 3 ± 0.05 k [from r 0 = R/(h/e 2 )], which is very close to sample's sheet resistance at room temperature R = 2.94 k . Furthermore, this value also describes the suppression of the superconducting critical temperature T c , following an expression originally proposed by Finkel'stein [37,38] (see also Appendix B). The suppression of T c is due to scattering and electron density fluctuations produced by the reduction of Coulomb screening.…”

“…We summarize some parameters obtained previously in both samples in Table I. In the Fig. 8, we provide the critical temperature versus sheet resistance in TiN films, from [38]. There, we calculated the dependence of T c using ln ( We reproduce data and model of Ref.…”

“…There, we calculated the dependence of T c using ln ( We reproduce data and model of Ref. [38]. We show the critical temperature vs the sheet resistance in different TiN samples as black points.…”

Dynamical instability of the electric transport in superconductors

“…The measurements were taken on the titanium nitride (TiN) film having the thickness d = 7 nm, the sheet resistance in the normal state Ω ( σ n = 4.3⋅10 4 (Ω cm) −1 ) and the superconducting critical temperature T c = 3.06 K. The film was formed on the Si/SiO 2 substrate by the atomic layer deposition. Temperature dependence of the resistance of this film has been examined in 33 where it was shown that the film is quasi-2D in the considered temperature range. The sample was patterned into bridges 50 μ m wide and 250 μ m long.…”