Refractive Index Matching: A New Criterion for High-Temperature Superconducting Material Design — An Interface Engineering Route Based on Causal Set Gauge-Flow Theory (CSGFT)

作者：Yunquan Liu · 发表于：Zenodo (CERN European Organization for Nuclear Research) · 年份：2026 · DOI：10.5281/zenodo.22058968 · 研究领域：Physics of Superconductivity and Magnetism、Heat Transfer and Boiling Studies、Solidification and crystal growth phenomena

Background: Since the discovery of cuprate high-temperature superconductors in 1986, breakthroughs in superconducting materials have long relied on experimental trial-and-error, lacking a simple, unified, and experimentally guidable material screening criterion. The conventional BCS theory is highly successful in explaining conventional superconductors, but its applicability in high-temperature superconducting systems has long been questioned. Interface-enhanced superconductivity (e.g., FeSe/SrTiO₃) has revealed the critical role of interface effects, yet a unified predictive framework for "which substrate-film combination can produce high-temperature superconductivity" remains absent. Methods: Based on Causal Set Gauge-Flow Theory (CSGFT), this paper proposes an experimentally testable phenomenological criterion: the superconducting transition temperature of a thin film is positively correlated with the substrate-film refractive index matching degree. In the CSGFT framework, the refractive index is a direct measure of the effective flux density in a medium, n=√(ρ_J^eff/ρ_J^vac); superconducting condensation corresponds to the collective phase coherence of closed circulating current clusters. This paper derives the quantitative relationship between refractive index matching degree and T_c (including lattice mismatch correction), and validates it using publicly available experimental data of FeSe thin films on different substrates (SrTiO₃, MgO, sapphire, Si). Results: (1) The ...