High-Temperature Superconductors: Recent Advances in Mechanisms and Persistent Challenges

Abstract

This review synthesizes cutting-edge developments in high-temperature superconductivity (HTS), focusing on unresolved pairing mechanisms and technological hurdles. Since the discovery of cuprates (1986), iron-based superconductors (2008), and record-breaking hydrides (T_c ≈ 288 K at 267 GPa), HTS research has expanded dramatically. Despite progress, a unified theory for unconventional pairing in cuprates and iron-based systems remains elusive. We analyze competing mechanisms—spin/orbital fluctuations, phonon-mediated interactions, and intertwined orders—highlighting the pseudogap phase enigma in cuprates. Recent breakthroughs include room-temperature hydrides, nickelate superconductors, and interface-engineered systems. However, persistent challenges include material heterogeneity, vortex pinning limitations, grain boundary issues in practical conductors, and the quest for ambient-pressure room-temperature superconductivity. Bridging fundamental theory with materials engineering is crucial for transformative applications.