Interplay between the glassy transition and granular superconductivity in organic materials

Abstract

It is known that some (BEDT−TTF)2X layered organic superconductors undergo a glassy transition near 80 K. Our purpose is to exploit quenched disorder to obtain insights on both the superconducting state (T⩽12K) and the glassy transition by studying the superconducting properties as functions of annealing time (ta) and temperature (Ta) around 80 K. The main results on the fully deuterated κ−(BEDT−TTF)2Cu[N(CN)2]Br compound are as follows: (i) The data can be described by a percolation cluster model. (ii) At short time scales, the clusters grow with ta following a power law. (iii) At large time scales the clusters grow toward a thermodynamic state following a stretched exponential law ∝{1−exp[−(t∕τ)β]} with β varying from about 0.5 to 1 in our Ta range (65–110 K). (iv) The relaxation time follows an Arrhenius law τ(T)=τ0exp(U∕T) with U≈2660K and 1∕τ0≈2×1013s−1. (v) The asymptotic magnetization fits with a scaling law ∝(Ta−Tg)−n with Tg≈55K and n≈3.2. The results are consistent with a Ising spin-glass-like model.

Source-reported materials — not catalogue approval

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