Microscopic origin of unconventional superconductivity in Re-based superconductors
Determine the microscopic origin of unconventional superconductivity and time-reversal-symmetry-breaking phenomena reported in Re-based superconductors, including the respective roles of strong spin-orbit coupling, structural complexity, chemical disorder, and the intrinsic electronic character of rhenium.
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Although generally brittle, $\sigma$-phase compounds exhibit high mechanical hardness and remarkable compositional flexibility, making them relevant for both functional and structural materials research . Superconductivity has been reported in numerous transition-metal $\sigma$-phase compounds , where the superconducting transition temperature ($T_c$) is strongly correlated with the electronic density of states and valence electron concentration . However, the narrow compositional stability of many $\sigma$-phase compounds has hindered systematic investigations of how chemical substitution, electronic structure, and lattice disorder collectively influence superconductivity. Consequently, material systems that retain the same $\sigma$-phase framework while allowing controlled variations in composition remain scarce. Among these materials, Re-based superconductors are of particular interest because several members of this family have been reported to exhibit unconventional superconductivity and time-reversal symmetry breaking, although the microscopic origin of these phenomena remains unresolved .