Anisotropic Hc2, thermodynamic and transport measurements, and pressure dependence of Tc in K2Cr3As3 single crystals

We present a detailed study of single crystalline K2Cr3As3 and analyze its thermodynamic and transport properties, anisotropic Hc2(T), and initial pressure dependence of Tc. In zero field, the temperature-dependent resistivity is metallic. Deviation from a linear temperature dependence is evident below 100 K and a T3 dependence is roughly followed from just above Tc (∼10K) to ∼40K. Anisotropic Hc2(T) data were measured up to 140 kOe with field applied along and perpendicular to the rodlike crystals. For the applied field perpendicular to the rod, Hc2(T) is linear with a slope ∼-70 kOe/K. For field applied along the rod, the slope is about -120 kOe/K below 70 kOe. Above 70 kOe, the magnitude of the slope decreases to ∼-70 kOe/K. The electronic specific heat coefficient γ, just above Tc, is 73 mJ/mol K2; the Debye temperature ΘD is 220 K. The specific heat jump at the superconducting transition ΔC∼2.2γTc. Finally, for hydrostatic pressures up to ∼7 kbar, Tc decreases under pressure linearly at a rate of -0.034K/kbar.