Plasmons in Unconventional Superconductivity and Topological Quantum Systems: From Fese-Based Superconductors to Topological Insulator Heterostructures

Plasmons, as collective oscillations of free electrons in solids, exhibit characteristics of both light and electrons, and demonstrate rich novel physical properties and functional application prospects in low-dimensional quantum systems. This article provides a systematic discussion of the role of plasmons in unconventional superconductivity and topological quantum materials. In the FeSe-based high-temperature superconducting system, we proposed an interfacial dynamical polaron model for the monolayer FeSe/SrTiO₃ system, clarifying that the oxide substrate enhances electron pairing within the FeSe layer through electron-phonon coupling. Furthermore, we established a polaron-bipolaron two-fluid model to explain the anomalous electrical transportin (Li₁₋ₓFeₓ)FeSe films, and proposed a "phonon + plasmon" multi- channel pairing mechanism, successfully explaining the non-monotonic evolution of Tc with carrier concentration in monolayer FeSe/STO, and predicting the isotope effect and plasmon-induced replica bands under multi-channel pairing. In topological quantum systems, we established an effective coupling model between topological surface states and two-dimensional electron gas, predicting gap opening in novel interband plasmons induced by band inversion and Dirac plasmons; two newly tunable plasmon modes were discovered in graphene/topological insulator heterostructures, and a novel probing approach based on inverting the topology of the system through plasmon modes was proposed by analogy with the bulk-boundary correspondence. This article concludes with a summary of the limitations of the innovations and an outlook on the development directions of this field.