Reemergence of superconductivity in pressurized quasi-one-dimensional superconductor ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$

Here we report a pressure-induced reemergence of superconductivity in a recently discovered superconductor ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$, which is an experimental case observed in quasi-one-dimensional superconductors. We find that, after full suppression of the ambient-pressure superconducting (SC-I) state at 8.7 GPa, an intermediary nonsuperconducting state sets in and prevails to the pressure up to 18.2 GPa, however, above this pressure a different superconducting (SC-II) state appears unexpectedly. High pressure x-ray diffraction measurements demonstrate that the pressure-induced dramatic change of the lattice parameter $c$ contributes mainly to the emergence of the SC-II state. Combined with the theoretical calculations on band structure, our results suggest that the reemergence of superconductivity is associated with the change of the complicated interplay among different orbital electrons, driven by the pressure-induced anisotropic change of the lattice.

Figure 1

(a) Resistance as a function of temperature for quasi-one-dimensional superconductor ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$ at ambient pressure. The inset displays a polycrystalline sample's image taken by a scanning electron microscope (SEM). The “single wire” seen in the SEM image composes of many smaller wires, therefore these wirelike objects are microcrystals. (b)–(d) Temperature dependence of the resistance in the pressure range of 1.2–8.7 GPa, 8.7–18.2 GPa, and 18.2–47.4 GPa, respectively. The insets of (b) and (d) display enlarged views of the resistance in the low temperature regime.

Figure 2

Temperature dependence of resistance under different magnetic fields for ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$ measured at 19.6 GPa (a) and 41.8 GPa (b), respectively. (c) Plot of superconducting transition temperature $T_c$ versus critical field ($H_{\mathrm{c}2}$) for ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$ at 19.6 GPa and 41.8 GPa, respectively. The dashed lines represent the Ginzburg-Landau (GL) fits to the data of $H_{\mathrm{c}2}$.

Figure 3

X-ray diffraction patterns collected in the pressure range of 3.8–51.6 GPa for ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$. The right panel schematically shows the evolution of the preferred orientation of the wirelike samples under pressures. SC-I and SC-II stand for the ambient-pressure superconducting state and the reemerged supercnducting states, respectively. NSC represents a nonsuperconducting state. The green arrow marks the position of the (002) peak.

Figure 4

Superconductivity, crystal, and electronic structure information for the qausi-one-dimensional superconductor ${\mathrm{K}}_2{\mathrm{Mo}}_3{\mathrm{As}}_3$. (a) Pressure-temperature phase diagram. (b) Pressure dependence of lattice parameters and volume (see inset). (c) Plots of percentage of the density of state (P-DOS) contributed by the ${d_z}^2$, $p_x$, and $p_y$ orbitals versus pressure.