Resistive transition in disordered superconductors with varying intergrain coupling

Abstract

The effect of disorder is investigated in granular superconductive materials with strong and weak links. The transition is controlled by the interplay of the tunneling g and intragrain g intr conductances, which depend on the strength of the intergrain coupling. For g ≪ g intr , the transition involves first the grain boundary, while for g ∼ g intr the transition occurs into the whole grain. The different intergrain coupling is considered by modelling the superconducting material as a disordered network of Josephson junctions. Numerical simulations show that on increasing the disorder, the resistive transition occurs for lower temperatures and the curve broadens. These features are enhanced in disordered superconductors with strong links. The different behaviour is further checked by estimating the average network resistance for weak and strong links in the framework of the effective medium approximation theory. These results may be relevant to shed light on long standing puzzles as: (i) enhancement of the superconducting transition temperature of many metals in the granular states; (ii) suppression of superconductivity in homogeneously disordered films compared to standard granular systems close to the metal-insulator transition; (iii) enhanced degradation of superconductivity by doping and impurities in strongly linked materials, such as magnesium diboride, compared to weakly-linked superconductors, such as cuprates.

Modulation of transport properties of optimally doped La1.85 Sr0.15 CuO4 thin films via electric field modification of the grain boundaries

“…We speculate that the field‐induced shrinking of the size of superconducting domains may trigger size effects at a certain point. This possibly explains the sudden onset of the foot feature for V g > 2 V. It is notable that the foot feature also resembles the effects seen in previous work, in which reduced dimensions of the superconducting materials resulted in a similar trend below T c . Ponta et al have suggested that a resistive transition is possible to model by varying the inter‐grain coupling , while others have demonstrated size modulation and proximity effect on such coupling .…”

“…Severe hole depletion from the grain boundaries may lead to an interfacial insulating state such that the conductivity across the grain boundaries may be explained via variable range hopping, where the electron–electron interaction differs as compared to that where enough free carriers are available (such as deep within the grains) . Also, by electrostatically modifying the film, we enter into a regime where Coulomb interaction effects and mesoscopic fluctuations are no longer negligible . Therefore, we expect that the charges driven by the source–drain voltage into a grain boundary from the grains experience strong scattering.…”

“…This leads to modulation of the coupling between the grains and shrinks the superconducting domains, which can further lead to the appearance of size effects. by varying the inter-grain coupling [29], while others have demonstrated size modulation and proximity effect on such coupling [32]. We can think of a situation in which the overall transport properties of the device are the sum of those resulting from different superconducting grains, i.e.…”

Substrate mediated nitridation of niobium into superconducting Nb2N thin films for phase slip study

“…In this case, the macroscopic superconductivity is established progressively through the Josephson proximity coupling effect among the locally disconnected superconducting grains possessing dimensional dependent distribution of critical temperature. We emphasize that disorder induced inhomogeneity 19 , finite size effect (FSE) for quasi zero-dimensional (0D) grains and the phase fluctuation are the main reasons behind the wide transition and resistive tailing. Besides, the appearance of PSLs in the IVC s and their evolution with film thickness indicate that disordered superconducting Nb 2 N can be of future interests in the field of PS based studies and applications.…”

Monetary Incentives in Italian Public Administration: A Stimulus for Employees? An Agent-Based Approach

“…In order to address such investigation, the paper presents an agent-based model and simulation based on empirical data collected by questionnaires. Simulation is a useful tool to investigate complex systems in many different fields such as engineering, physics, mathematics, and economics and is also becoming an increasingly significant methodological approach in organizations and strategy and public management field [11][12][13][14][15][16]. Among the different simulation models, the agent-based approach is very useful to investigate complex systems and networks characterized by a large number of simple interacting units [17][18][19][20][21][22][23][24][25][26].…”