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Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-2D organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br: quest for instrinsic scattering contributions

Strack, C.; Akinci, C.; Pashchenko, V.; Wolf, B.; Uhrig, E.; Assmus, W.; Lang, M.; Schreuer, J.; Wiehl, L.; Schlueter, J. A.; Wosnitza, J.; Schweitzer, D.; Müller, J.; Wykhoff, J.


Resistivity measurements have been performed on a low (LR)- and high (HR)-resistance variant of the κ-(BEDT-TTF)2Cu[N(CN)2]Br superconductor. While the HR sample was synthesized following the standard procedure, the LR crystal is a result of a somewhat modified synthesis route. Judging by their residual resistivities and residual resistivity ratios, the LR crystal is of distinctly superior quality. He-gas pressure was used to study the effect of hydrostatic pressure on the different transport regimes for both variants. The main results of these comparative investigations are (i) a significant part of the inelastic-scattering contribution, which causes the anomalous ρ(T) maximum in standard HR crystals around 90 K, is sample dependent, i.e., extrinsic in nature; (ii) the abrupt change in ρ(T) at T* ≈ 40 K from a strongly temperature-dependent behavior at T>T* to an only weakly T-dependent ρ(T) at T2 dependence at low temperatures, i.e., for Tc≤T≤T0, although with strongly sample-dependent coefficients A and upper bounds for the T2 behavior measured by T0. Provided that there are no differences in the Fermi surface between both variants—the present experiments give no indications for such differences—the latter result is inconsistent with the T2 dependence originating from coherent Fermi-liquid excitations.


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