Magnetic and electronic phase diagram and superconductivity in the organic superconductorsκ−(ET)2X

Abstract

The magnetic susceptibility of the organic superconductors -(h8 or d8-ET) 2 X, XϭCu(NCS) 2 and Cu͓N(CN) 2 ͔Br has been studied. A metallic phase below T*ϭ37-38 K for XϭCu͓N(CN) 2 ͔Br and 46 -50 K for XϭCu(NCS) 2 has an anisotropic temperature dependence of the susceptibility and the charge transport. Partial charge-density-wave or charge fluctuation is expected to coexist with the metallic phase instead of the large antiferromagnetic fluctuation above T*. The phase diagram and the superconductivity of -(ET) 2 X are discussed in connection with this phase.

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

“…Anomalous behavior around T * has been also identified in various thermal 7,20,21,25,26 , magnetic 27,28,29,30 , elastic 22 , and optical properties 31 . Various explanations have been proposed as to the nature of the T * anomaly, including the formation of a pseudo-gap in the density of states 27,28,29,32 , a crossover from a coherent Fermi liquid at low temperatures into a regime with incoherent excitations at high temperatures 4,14 , a density-wavetype instability 20,26,33 , as well as an incipient divergence of the electronic compressibility caused by the proximity to a Mott transition 5 .…”

“…Various explanations have been proposed as to the nature of the T * anomaly, including the formation of a pseudo-gap in the density of states 27,28,29,32 , a crossover from a coherent Fermi liquid at low temperatures into a regime with incoherent excitations at high temperatures 4,14 , a density-wavetype instability 20,26,33 , as well as an incipient divergence of the electronic compressibility caused by the proximity to a Mott transition 5 . The present resistivity results, which for the HR crystal confirm published data 21 , clearly demonstrate that the position of the T * anomaly is unaffected by the strength of the additional scattering contribution giving rise to the resistivity hump at intermediate temperatures, and thus marks an independent feature.…”

Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions:β″−(BEDT−TTF)Coldea1, Bangura2, Singleton3 et al. 2004Phys. Rev. B511210View full textAdd to dashboardCite

“…Moreover, the superconducting region in both ␤Љ and salts is surrounded by nonuniform or mixed phases. 8 The study of ␤Љ-(BEDT-TTF) 4 ͓(H 3 O)M (C 2 O 4 ) 3 ͔Y salts seems to emphasize the fact that very highly resistive samples and phenomena associated with quasiparticle localization ͑e.g., Anderson localization 62 ͒ and/or disorder 63 coexist with effects normally associated with ''good metals,'' such as Shubnikov-de Haas oscillations 64 and even superconductivity. 62 Furthermore, there is experimental evidence that the precursor to superconductivity may involve the coexistence of metallic and density-wave-like states, such as the case of ␤Љ-(BEDT-TTF) 2 SF 5 CH 2 CF 2 SO 3 ͑Ref.…”

Mott transition and superconductivity in the strongly correlated organic superconductorκ−(BEDT−TTF)2Cu[N(<

“…3,5,6,7,8 The relation and transitions among the various phases in the phase diagram have been studied extensively, both experimentally and theoretically. Several unique features have been found in association with the Mott transition.…”