Research progress of magnetic resonance wireless power transfer based on higher-order non-Hermitian physics

In recent years, wireless power transfer (WPT) leveraging parity-time (PT) symmetry has made significant progress , in terms of enhancing efficiency, transfer distance, and robustness. This paper overviews magnetic resonance WPT systems utilizing ideal, asymmetric, high-order, and anti-PT symmetry. The first section discusses the second-order PT symmetry, evolving from inductive to resonant WPT. Active tuning and nonlinear saturation gain techniques optimize frequency and spontaneously achieve efficient WPT. These methods improve transmission efficiency, especially with the change of dynamic transfer distance. The second section focuses on the third-order PT and anti-PT symmetry. The third-order PT systems maintain a fixed eigenfrequency, making stable energy transfer possible. Generalized PT symmetry harnesses bandgaps for further efficiency. The BIC in asymmetric systems reveals a pure real mode for stable WPT. The anti-PT symmetry's 'level pinning' maintains stability in dynamic changes. The final section summarizes high-order PT symmetry for long-range WPT. Heterojunction coupling and topologically non-trivial chains enhance efficiency and stability. Examples include long-range WPT via relay coils and directional WPT using asymmetric topological edge states. In summary, this review emphasizes the pivotal role of various forms of PT symmetry in improving the performance and reliability of magnetic resonance WPT systems. By improving transmission efficiency, range, and stability, these symmetries pave the way for wider applications in fields such as smart homes, medical devices, and electric vehicles. The synthesis of current research results provides valuable insights and references for the future development of WPT technology.