Superheating fields of semi-infinite superconductors and layered superconductors in the diffusive limit: structural optimization based on the microscopic theory

Abstract The superheating field H s mathvariant="normal">h of the Meissner state is thought to determine theoretical field-limit superconducting accelerator cavities. We investigate semi-infinite superconductors and layered structures in diffusive limit using well-established quasiclassical Green’s function formalism BCS theory. coupled Maxwell–Usadel equations are self-consistently solved obtain spatial distributions magnetic field, screening current density, penetration depth, pair potential, . For a superconductor limit, we $H_\mathrm{sh} = 0.795 H_{c0}$?> = 0.795 c 0 at temperature $T\to 0$?> T → Here, $H_{c0}$?> thermodynamic critical-field zero temperature. By laminating film (S) with thickness $d$?> d on (Σ), can engineer $H_\mathrm{sh}(d)$?> stretchy="false">( stretchy="false">) structure. When optimum $d_m$?> m , be larger than that simple made from S Σ materials: $H_\mathrm{sh}(d_m) \gt \max \{H_\mathrm{sh}^{\textrm{(S)}} H_\mathrm{sh}^{(\Sigma)} \}$?> sh > max { S , Σ } present study addresses calculation dirty heterostructure microscopic theory beginning end for first time, which contributes understanding surface engineering pushing up accelerating gradient cavities particle accelerators.