Nonlinear Seebeck effect in a model granular superconductor

Abstract

The change of the Josephson supercurrent density js of a weakly-connected granular superconductor in response to externally applied arbitrary thermal gradient ∇T (nonlinear Seebeck effect) is considered within a model of 3D Josephson junction arrays. For ∇T > (∇T )c, where (∇T )c is estimated to be of the order of ≃ 10 4 K/m for Y BCO ceramics with an average grain's size d ≃ 10µm, the weak-linksdominated thermopower S is predicted to become strongly ∇T -dependent.

Piezomagnetism and stress-induced paramagnetic Meissner effect in mechanically loaded high-T c granular superconductors

“…Namely, the sites in a 3D cubic lattice are assumed to move from their equilibrium positions according to the normalized (separable) distribution function f ( r ij R ij ) ≡ f r ( r ij )f R ( R ij ). As usual [8,10,11], it can be shown that the main qualitative results of this paper do not depend on the particular choice of the probability distribution function. For simplicity here we assume an exponential distribution law for the distance between grains, f r ( r) = f (x)f (y)f (z) with f (x j ) = (1/d)e −xj/d , and some short range distribution for the dependence of the center-of-mass probability f R ( R) (around some constant value D).…”

“…To give just a few recent examples, it is sufficient to mention paramagnetic Meissner effect [2][3][4][5] (PME) originated from a cooperative behavior of weak-links mediated orbital moments and found to be responsible for unusual aging effects [6] in high-T c granular superconductors (HTGS). Among others are also recently introduced thermophase [7,8] and piezophase [9] effects suggesting, respectively, a direct influence of a thermal gradient and an applied stress on phase difference between the adjacent grains. Besides, using a model of random overdamped Josephson junction arrays, two dual time-parity violating effects in HTGS have been predicted [10,11].…”

Influence of chemical pressure effects on nonlinear thermal conductivity of intrinsically granular superconductors

“…By analogy with a constant electric field E, a thermal gradient ∇T applied to a chemically induced JJA will cause a time evolution of the phase difference across insulating barriers as follows [15,17,18] …”

On the field-induced diaelastic effect in a small Josephson contact

“…For the explicit temperature dependence of I C (T) we use the analytical approximation of the BCS gap parameter (valid for all temperatures) [17], Δ(T) = Δ(0)tanh with Δ(0) = 1.76k B T C which governs the temperature dependence of the Josephson critical current (11) while the temperature dependence of the London penetration depth is governed by the two fluid model [28]:…”

“…In particular, a remarkable increase of the measurements technique resolution made it possible to experimentally detect such inter esting phenomena as flux avalanches [5], geometric quantization [6], flux driven oscillations of heat capacity [7], reentrant like behavior [8], manifesta tion of π contacts [9], R-C crossover [10], unusually strong coherent response [11], Josephson analog of the fishtail effect [12], geometric resonance and field induced Kosterlitz-Thouless transition [13]. Among the numerous theoretical predictions (still awaiting their experimental verification) one could mention electro and magnetostriction [14], field induced polarization effects [15], analog of magnetoelectric effect [16], nonlinear Seebeck effect and thermal con ductivity [17], stress induced effects [18], chemomag netism [19], magnetoinductance effects [20], implica tions of dipolar interactions for wireless connection between Josephson qubits [21] and for weakening of the Coulomb blockade [22], proximity induced superconductivity in graphene [23] and anomalous Josephson current in topological insulators [24].…”