Flipping of antiferromagnetic to superconducting states in pressurized quasi-one-dimensional manganese-based compounds

One of the universal features of unconventional superconductors is that the superconducting (SC) state is developed in the proximity of an antiferromagnetic (AFM) state. Unified understanding the interplay between these two states in different superconducting systems is one of the key issues to uncover the underlying physics of unconventional SC mechanism. Here, we report a pressure-induced superconductivity in the quasi-one-dimensional $\mathrm{Cs}{\mathrm{Mn}}_{6}{\mathrm{Bi}}_{5}$ compound that bears an AFM state at ambient pressure. The SC state appears at the critical pressure $({P}_{c})$ of $\ensuremath{\sim}12$ GPa and stabilizes up to $\ensuremath{\sim}27$ GPa. The high-pressure x-ray-diffraction measurements on $\mathrm{Cs}{\mathrm{Mn}}_{6}{\mathrm{Bi}}_{5}$ indicate that no structural phase transition occurs at the ${P}_{c}$, indicating that the AFM-SC transition is electronic in origin. By comparing the previous results of $A{\mathrm{Mn}}_{6}{\mathrm{Bi}}_{5}$ ($A=\mathrm{K}$, Rb), we identify that all members of the family possess the genetic flipping behavior of AFM-SC states at almost the same ${P}_{c}$, though their ambient-pressure unit-cell volumes vary quite differently. Our theoretical calculations suggest that the pressure-induced changes of partial density of state contributed by the ${d}_{yz}$ and ${d}_{xz}/{d}_{{z}^{2}}$ orbital electrons near Fermi energy may be associated with the origin of the flipping. These results provide a diverse picture of the connection between the AFM and SC states in the $3d--$ transition-metal compounds.