Complex evolution of the magnetic transitions and unexpected absence of bulk superconductivity in chemically precompressed NaMn6Bi5

Pressurized AMn6Bi5 (A = K, Rb, Cs) members have recently emerged as a new family of ternary manganesebased superconductors that exhibits a broad superconducting dome with a maximum critical temperature up to similar to 9.5 K adjacent to the long-range antiferromagnetic phase in their T-P phase diagrams. The analogous compound NaMn6Bi5, with a smaller A-site cation and lower antiferromagnetic transition temperatures T1 approximate to 46 K and T2 approximate to 52 K is expected to show superconductivity at lower pressures. By performing detailed highpressure electrical transport measurements on the chemically precompressed NaMn6Bi5 single crystals, we map out the complex evolution with pressure of its multiple magnetic transitions, which are eventually suppressed by pressures. Contrary to the expectation, the bulk superconductivity is absent near the magnetic quantum critical point, where we observed a weak decrease in resistance below 2.4 K in a narrow pressure range of 12 to 14.4 GPa from the measurements in a diamond anvil cell. The origin of this anomaly remains unclear, and it might be ascribed to the presence of filamentary superconductivity in analogy to other AMn6Bi5. These distinct results of NaMn6Bi5 with respect to other AMn6Bi5 members highlight the complexity of magnetism and its interplay with superconductivity in this family of quasi-one-dimensional compounds.

Automated summary

Pressurized AMn6Bi5 (A = K, Rb, Cs) compounds are a new family of ternary manganese-based superconductors that exhibit a broad superconducting dome with a maximum critical temperature up to similar to 9.5 K next to the long-range antiferromagnetic phase. The compound NaMn6Bi5, with a smaller A-site cation and lower antiferromagnetic transition temperatures T1 approximate to 46 K and T2 approximate to 52 K, is expected to show superconductivity at lower pressures. However, our high-pressure electrical transport measurements on chemically precompressed NaMn6Bi5 single crystals reveal the absence of bulk superconductivity near the magnetic quantum critical point, suggesting the presence of filamentary superconductivity.