Advances in Iron-Based Superconductors and Transformational Insights into Electron–Differential Phonon Coupling

Since the discovery of iron-based superconductors nearly two decades ago, significant advancements have been made, including the enhancement of the superconducting transition temperature (Tc) to above 100 K. However, the underlying pairing mechanism remains an unresolved enigma. In this article, we present experimental developments in iron-based superconductors, focusing on their unique properties and the complexities involved in their behavior. We discuss the recently announced electron–differential phonon coupling model, which aims to provide a framework to calculate the Tc of iron-based superconductors, but raises questions about its applicability to all iron-based superconductors. We selectively analyze several compounds within the major iron-based families to assess their compatibility with the electron–differential phonon coupling model. By comparing experimental data with theoretical predictions, we identify which superconductors align with the model and which do not. Furthermore, our findings reveal several key reasons behind the discrepancies in calculating Tc for those iron-based materials that fall outside the theoretical expectations. Despite this, the pairing mechanism of iron-based superconductors remains an open question.