Superconducting Metal Gyroids: Block Copolymer Self-assembly for Mesoscale Engineering of Quantum Metamaterials

A growing body of work has demonstrated emergent properties in mesostructured quantum materials. Such quantum metamaterials have recently been generated via block copolymer (BCP) self-assembly (SA), which imparts tunable control of mesoscopic architecture. In this work we use BCP SA to structure direct polysilazanes and create mesoporous silicon oxynitride ceramics with a cubic co-continuous double gyroid structure. These ceramic templates are backfilled with molten indium under high pressures. X-ray scattering and electron microscopy demonstrate high fidelity backfilling in the resulting nanocomposites, a substantial advancement in BCP SA directed metals. Analysis of superconducting indium reveals that the BCP architecture dictates quantum properties: the superconducting coherence length decreases from 360 nm to 20 nm, roughly the diameter of a gyroid strut. This leads indium to switch from a type-I to type- II superconductor, with an enhanced critical field and evidence of vortices arrayed on the order of the gyroid lattice size. Results suggest that BCP SA approaches to quantum metamaterials opens a rich area for investigation of mesostructure-property correlations. Further, polymer solution based fabrication yields benefits beyond traditional ultrahigh vacuum based methods.