Rotation manipulation of high-order PT-symmetry for robust wireless power transfer

Magnetic resonance coupling plays an important role in the non-radiative wireless power transfer without cables. However, the basic near-field coupling also has some key limitations on the resonance wireless power transfer (WPT). On the one hand, when the transfer distance is short, the eigenfrequencies of the WPT system will split because of the strong near-field coupling between the resonance transmitter and receiver. On the other hand, although the working frequency is fixed for the long-distance case, the transfer efficiency will be significantly dropped for the weak coupling strength. Therefore, a long-captivated problem of the resonance WPT systems is that it is difficult to balance the fixed working frequency and high efficiency of the devices. In this work, we put forward the composite transmitter with a pair of resonance coils of different size. By assisting the rotational degrees of freedom in the composite transmitter, a high-order parity-time-symmetric non-Hermitian system can be established. Especially, in contrast to the conventional resonance WPT scheme, the robust WPT can maintain fixed working frequency and efficiency over a varying transfer distance in the optimized WPT system with composite transmitter, since this eigenfrequency is insensitive to the operational conditions. Our findings demonstrate that the composite transmitter possesses better performance for WPT than its single counterpart, offering the opportunities for engineering novel designer electromagnetic transfer states with unique robustness.