Synthesis of Chiral Three-Dimensionally Ordered Mesoporous Superconducting Niobium Nitride Gyroids using Block Copolymer Self-Assembly

Superconductors with three-dimensional (3D) mesoscale order and porosity are expected to have properties very different from their bulk counterparts. For example, flux pinning in mesoscale lattices may result in enhanced upper critical fields or novel angle-dependent behavior, and a chiral mesostructure might allow nonlinear magnetoelectric couplings or other properties. The exploration of these properties has been limited by a lack of versatile, tunable synthetic approaches to such 3D mesoscale ordered superconductors. We report the synthesis of gyroidal mesoporous niobium nitride from block copolymer self-assembly derived mesoporous niobium oxide with subsequent high temperature treatment in flowing ammonia gas. The resulting materials have a Tc of about 7.8 K and a mesoscale lattice with the I4₁32 (alternating gyroid) structure with lattice spacings between 27 and 36 nm. Recent efforts to improve the superconducting properties of these materials and to expand the accessible range of length scales and structures will be discussed. We expect block copolymer-inorganic hybrid co-assembly will prove to be a versatile platform for exploration of the impacts of mesoscale order and porosity on the magnetic properties of superconductors.