Superconductivity, incoherence and Anderson localization in the crystalline organic conductor (BEDT-TTF)3Cl2$middot$ 2H2O at high pressures

Abstract

Abstract. The conducting properties of the pressure-induced, layered organic superconductor (BEDT-TTF) 3 Cl 2 ·2H 2 O have been studied at 13.5 and 14.0 kbar using low temperatures, high magnetic fields and two-axis rotation. An upper critical field that is significantly larger than that expected from the Pauli paramagnetic limit is observed when the field is applied parallel to the conducting layers. The angle dependent magnetoresistance suggests incoherent transport between the conducting layers at both pressures and the observed negative magnetoresistance at 13.5 kbar can be explained by considering Anderson localization within the layers. Further application of pressure destroys the effects of localization.

Inhomogeneous superconductivity in condensed matter and QCD

“…This upturn and a first-order transition below the critical field have been observed in the organic compound -(BEDT-TTF) 2 Cu(NCS) 2 , a quasi-twodimensional organic superconductor examined by a number of authors Houzet and Buzdin, 2000;Ishiguro, 2000;Singleton et al, 2000Singleton et al, , 2001Symington et al, 2001). A similar compound is studied by Goddard et al (2002). These studies give some evidence of the formation of the LOFF state.…”

“…Condensation in this channel might be relevant for low-density bulk matter such as the dilute nuclear matter in supernovas. On the other hand, there is no evidence of large-gap isospin singlet pairing in ordinary nuclei, which might be explained by the presence of a spin-orbit interaction (Goodman, 1999;MartinezPinedo et al, 1999). Sedrakian and Lombardo (2000) study the dependence of the gap on both the isospin asymmetry ␣ np ϭ( n Ϫ p )/ and the temperature, using realistic nuclear interactions.…”

“…Their theory was based on the fundamental theorem of Cooper (1956), which states that, for a system of many electrons at small T, any weak attraction, no matter how small it is, can bind two electrons together, forming the so-called Cooper pair. Subsequently Gor'kov (1959) realized that the Ginzburg-Landau theory was equivalent to the BCS theory around the critical point, and this result vindicated the Ginzburg-Landau theory as a masterpiece in physics. Furthermore, Gor'kov proved that the fundamental quantities of the two theories, i.e., the BCS parameter gap ⌬ and the Ginzburg-Landau wave function were related by a proportionality constant, so that could be thought of as the Cooper-pair wave function in the center-of-mass frame.…”

“…In Sec. II we begin by describing the general formalism based on the Nambu-Gor'kov equations (Gor'kov, 1959;Nambu, 1960). As shown by Polchinski (1993) using the renormalization-group approach, excitations at the Fermi surface can be described by an effective-field theory.…”

Robust superconducting state in the low-quasiparticle-density organic metalsβ″−(BEDT−TTF)4[(Bangura1, Coldea2, Singleton3 et al. 2005Phys. Rev. B

“…For T ജ 10 K , zz is initially ͑B Շ 3 T͒ proportional to B 2 ; at higher fields, the resistivity varies approximately linearly with B. Such behavior is entirely typical of metallic chargetransfer salts 21,27 and other layered systems; 28,29 the magnetoresistance is presumably mainly associated with the metallic regions of the samples.…”