Phase diagram of superconductivity and spin density wave in (DMET) 2Au(CN) 2

Abstract

The pressure-temperature phase diagram of (DMET) 2Au(CN) 2 is determined through electrical resistivity measurement. At ambient pressure, (DMET) 2Au(CN) 2 is metallic at room temperature and undergoes phase transition into spin density wave (SDW) at 22 – 28 K. With the increase of pressure, SDW is suppressed, vanishing above 3.5 kbar. The superconductivity is present between 1.5 kbar and 5.5 kbar. Thus, the pressure region in which both SDW and superconductivity are observed is as wide as ∼ 4 kbar, which is much wider than the salts ever known. In the SDW state, in contrast to the phases of TMTSF salts, the divergence of electrical resistivity is incomplete, which must be due to a Fermi surface still remaining in the SDW state. Also observed is a sharp dip in the temperature dependence of electrical resistivity at 180 K at ambient pressure, suggesting a phase transition, whose temperature increases with pressure.