We investigate low-temperature transport properties of thin TiN superconducting films in the vicinity of the disorder-driven superconductor-insulator transition. In a zero magnetic field, we find an extremely sharp separation between superconducting and insulating phases, evidencing a direct superconductor-insulator transition without an intermediate metallic phase. At moderate temperatures, in the insulating films we reveal thermally activated conductivity with the magnetic field-dependent activation energy. At very low temperatures, we observe a zero-conductivity state, which is destroyed at some depinning threshold voltage VT . These findings indicate formation of a distinct collective state of the localized Cooper pairs in the critical region at both sides of the transition.An early suggestion that tuning disorder strength can cause a direct superconductor-insulator transition (SIT) in two-dimensional systems [1] triggered explosive activity in experimental studies of superconductor films [2]. Experimentally, the SIT can be induced by decreasing the film thickness [3] and/or, close to the critical thickness, also by the magnetic field [4]. These scenarios are commonly referred to as disorder-driven SIT (D-SIT) and magnetic-field driven SIT. Recent studies on the Binduced insulator revealed several striking features: a magnetic-field-dependent thermally activated behavior of the conductivity [5] and a threshold response to the dc voltage [6], indicating the possible formation of a distinct collective insulating state. Importantly, these findings refer to the films belonging to the superconducting side of the D-SIT. This rises the question of whether the above findings are specific only to the superconducting side of the D-SIT or a characteristic feature of the whole critical region including both the insulating and superconducting sides of the D-SIT.In this Letter we focus on the insulating side of the disorder-driven superconductor-insulator transition in TiN films. The transition itself turns out to be exceptionally sharp. At zero and low magnetic fields we find thermally activated behavior of the conductivity. A positive magnetoresistance and a distinct threshold behavior in the low-temperature I-V characteristics persist on the insulating side of the D-SIT. Our results clearly indicate that, in the vicinity of the D-SIT, the response to applied magnetic and/or electric fields, is the same irrespective of whether the underlying ground state is superconducting or insulating.The 5-nm thick TiN films were grown by atomic layer chemical vapor deposition onto a Si/SiO 2 substrate. The samples for transport measurements were patterned into Hall bridges using conventional UV lithography and subsequent plasma etching. To increase sheet resistances (R ) without introducing structural changes, the films were thinned by an additional soft plasma etching. Electron transmission micrographs and diffraction patterns revealed a polycrystalline structure in both initial and etched films, the interfaces separating densely-p...
We investigate the effects of inelastic cotunneling on the electronic transport properties of gold nanoparticle multilayers and thick films at low applied bias, inside the Coulomb blockade regime.We find that the zero-bias conductance, g 0 (T ), in all systems exhibits Efros-Shklovskii-type variable range hopping transport. The resulting typical hopping distance, corresponding to the number of tunnel junctions participating in cotunneling events, is shown to be directly related to the power law exponent in the measured current-voltage characteristics. We discuss the implications of these findings in light of models on cotunneling and hopping transport in mesoscopic, granular conductors.
We generalize the Beliaev-Popov diagrammatic technique for the problem of interacting dilute Bose gas with weak disorder. Averaging over disorder is implemented by the replica method. Low energy asymptotic form of the Green function confirms that the low energy excitations of the superfluid dirty Boson system are sound waves with velocity renormalized by the disorder and additional dissipation due to the impurity scattering. We find the thermodynamic potential and the superfluid density at any temperature below the superfluid transition temperature and derive the phase diagram in temperature vs. disorder plane.Superfluidity in random environments enjoys a long standing yet intense attention. The effect of disorder on the behavior of systems possessing long-range correlations is central to contemporary condensed matter physics, and superfluid Bose gas offers an exemplarily unique and accessible tool for both experimental and theoretical researches. One of the fascinating properties of such systems is their ability to maintain superfluidity (i.e. long range correlations) even in the strongly disordered environment. He 4 , for example, remains superfluid when absorbed in porous media [1]. The problem of influence of disorder on superfluidity (and on its close analogsuperconductivity) has been under extensive theoretical attack (see seminal works [2,3]) and remarkable progress in qualitative understanding of disordered Bose systems was achieved. Recent papers [4,5] discussed a continuum model of the dilute interacting Bose gas in a random potential. The advantages of this model are that (i) it is microscopically related to the original problem and (ii) it is very well understood in the clean limit. The proposed model describes, in particular, the quasiparticle dissipation and depletion of superfluidity at zero temperature and marked an important step towards quantitative description of disordered Bose systems.In this Letter, building on the model of Refs. [4,5], we develop a systematic diagrammatic perturbation theory for the dilute Bose gas with weak disorder at finite temperatures below the superfluid transition temperature T s . We obtain disorder corrections to the thermodynamic potential which completely determine thermodynamic properties of the superfluid system. We derive for the first time the disorder-induced shift of T s resulting from disorder scattering of quasiparticles with energy ǫ ∼ T . We find that the superfluid density decreases monotonically with the temperature. This completely agrees with the experimental data, while being in some contradiction with the theoretical result of Ref.[4] where a non-monotonic temperature dependence of superfluid density dependence was claimed. In the limit T → 0 our theory reproduces all the results of Refs. [4,5].The model. The starting point of our model is the Lagrangian density:where ϕ = ϕ(r, τ ) is the field representing Bose particles, r is the real space coordinate, τ is the Matsubara time and u(r) is the disorder potential. As usual we consider a soft intera...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.