Synthesis and physical properties of the theoretically predicted spin-triplet superconductor Li0.9Mo6O17

We report the single crystal growth and characterization of the quasi-one-dimensional superconductor Li_0.9Mo₆O₁₇ via temperature-gradient flux method. The grown single crystals show a clear ab plane identified by the x-ray diffraction (XRD) pattern. Temperature dependent resistivities reveal a metallic to semiconducting crossover at T_M = 24 K followed by a superconducting transition at T_c = 2.2 K for ${\rho }_a$ and ${\rho }_c$. In addition, the upper critical fields demonstrate a large anisotropy with $H_{c2}^b>H_{c2}^a>H_{c2}^c$ both at ${\rho }_a$ and ${\rho }_c$. Particularly, an upper critical field $H_{c2}^b$ of about 16.2 T at zero temperature limit was deduced from the field dependence of resistivity measurements, which is notably larger than the estimated Pauli paramagnetic limit 3.1 T and supports the existence of the spin-triplet superconducting pairing and unconventional superconductivity in Li_0.9Mo₆O₁₇. The XRD, resistivities and upper critical field measurements all imply a high quality of the as-grown Li_0.9Mo₆O₁₇ samples. Furthermore, the interlayer and in-plane magnetoresistivity (MR) up to 60 T reveal the possible phase transition driven by the density-wave gap suppression and Zeeman split effect in the high field state.