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

Abstract

We present a detailed study of single crystalline ${\mathrm{K}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ and analyze its thermodynamic and transport properties, anisotropic $H_{c2}\left(T\right)$, and initial pressure dependence of $T_c$. In zero field, the temperature-dependent resistivity is metallic. Deviation from a linear temperature dependence is evident below 100 K and a $T^3$ dependence is roughly followed from just above $T_c$ ($\sim 10\mathrm{K}$) to $\sim 40\mathrm{K}$. Anisotropic $H_{c2}\left(T\right)$ 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, $H_{c2}\left(T\right)$ is linear with a slope $\sim -70$ 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 $\sim -70$ kOe/K. The electronic specific heat coefficient $\gamma$, just above $T_c$, is 73 mJ/mol ${\mathrm{K}}^2$; the Debye temperature ${\Theta }_D$ is 220 K. The specific heat jump at the superconducting transition $\Delta C\sim 2.2\gamma T_c$. Finally, for hydrostatic pressures up to $\sim 7$ kbar, $T_c$ decreases under pressure linearly at a rate of $-0.034\mathrm{K}/\mathrm{kbar}$.