Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-two-dimensional organic superconductorκ−(BEDT−TTF)2Cu[N

Abstract

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. According to 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 T < T * is unaffected by this scattering contribution and thus marks an independent property, most likely a second-order phase transition, (iii) both variants reveal a ρ(T) ∝ AT 2 dependence at low temperatures, i.e. for Tc ≤ T ≤ T0, although with strongly sample-dependent coefficients A and upper bounds for the T 2 behavior measured by T0. The latter result is inconsistent with the T 2 dependence originating from coherent Fermi-liquid excitations.

Mott-Anderson Transition in Molecular Conductors: Influence of Randomness on Strongly Correlated Electrons in the κ-(BEDT-TTF)2X System

“…Figure 4 shows the temperature dependence of κ-(BEDT-TTF) 2 X with X = Cu(NCS) 2 3 irradiated by X-ray. At the start with the superconductor X = Cu(NCS) 2 and Cu[N(CN) 2 ]Br before irradiation, the resistivity shows the characteristic behavior reported previously [41]: a broad resistivity hump at 100 K, a crossover around T * from a bad to good metallic state at low temperature where the resistivity follows ρ(T) = ρ 0 + AT 2 and the superconducting transition at T c~1 0 K (X = Cu(NCS) 2 ) and 11 K (X = Cu[N(CN) 2 ]Br). However, X-ray irradiation of the samples changes the behavior of the resistivity drastically.…”

In-plane superfluid density and microwave conductivity of the organic superconductorκ-(BEDT-TTF)2Cu[N(CN)2]Br: Evidence forMilbradt1, Bardin2, Truncik3 et al. 2013Phys. Rev. B354461View full textAdd to dashboardCite

“…It is important to note that most previous measurements of resistivity in κ-(ET) 2 Cu[N(CN) 2 ]Br have been measured perpendicular to the highly conducting planes due to difficulties in obtaining properly calibrated in-plane resistivity data. [29][30][31] By providing some of the first reliable measurements of this quantity, the microwave experiment also allows us to perform important tests of dynamical mean field theory (DMFT) [32][33][34] and of the predicted Kadowaki-Woods ratio in these materials. 35 Single crystals of κ-(ET) 2 Cu[N(CN) 2 ]Br were grown by controlled electrocrystallization in a dichloromethane solution containing 8% (vol.)…”

“…29 Properly calibrated measurements of ρ are difficult to make by conventional means in the κ-(ET) 2 X compounds, due to their large electrical anisotropy. 30,31 From the new microwave data, a number of key quantities can now be extracted. In addition, we can perform a test of DMFT, which provides a powerful framework for understanding the normal state of organic superconductors.…”

Magnetic and Electric Properties of Organic Conductors Probed by 13C-NMR Using Selective-Site Substituted Molecules

“…However, this salt does not behave as a simple Fermi liquid at high temperatures. The electrical resistance of κ-(BEDT-TTF) 2 Cu(NCS) 2 shows semiconductive behavior above 80 K and, it steeply decreases showing T 2 dependence below 30 K [64]. This behavior is a feature of all κ-type salts [15].…”