Transport properties and structural features of the ambient-pressure superconductorκ′−(BEDT−TTF)2Cu[N(CN)2]Cl

Abstract

The crystal structure and low-temperature transport properties of the recently synthesized ${\ensuremath{\kappa}}^{\ensuremath{'}}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{C}\mathrm{N})}_{2}]\mathrm{Cl}$ radical cation salt are investigated. The crystals exhibit metallic conductivity and are ambient-pressure superconductors with critical temperature in the range $(11.3--11.9)\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The crystals show some distinctions in structure as compared to that of the Mott insulator $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{C}\mathrm{N})}_{2}]\mathrm{Cl}$: smaller size of the unit cell and deficiency in the occupancy of the copper positions. Anisotropy of superconducting properties as well as a nontrivial temperature dependence of the upper critical field were observed.