Anisotropic $H_{c2}$, thermodynamic and transport measurements, and pressure dependence of $T_{c}$ in K$_{2}$Cr$_{3}$As$_{3}$ single crystals

TL;DR

This study investigates the anisotropic superconducting properties, thermodynamics, and pressure effects on K$_{2}$Cr$_{3}$As$_{3}$ single crystals, revealing detailed behavior of $H_{c2}$, specific heat, and $T_c$ under various conditions.

Contribution

It provides comprehensive measurements of anisotropic $H_{c2}$, thermodynamic properties, and pressure dependence of $T_c$ in K$_{2}$Cr$_{3}$As$_{3}$, offering new insights into its superconducting characteristics.

Findings

$H_{c2}$ is highly anisotropic with different slopes for field orientations.

The specific heat jump at $T_c$ is approximately 2.2 times $\gamma T_c$.

$T_c$ decreases linearly with pressure at -0.034 K/kbar.

Abstract

We present a detailed study of single crystalline K$_{2}$Cr$_{3}$As$_{3}$ and analyze its thermodynamic and transport properties, anisotropic $H_{c2}(T)$, 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 K) to $\sim$ 40 K. Anisotropic $H_{c2}(T)$ data were measured up to 140 kOe with field applied along and perpendicular to the rod-like crystals. For the applied field perpendicular to the rod, $H_{c2}(T)$ 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 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 K/kbar.