arXiv subjects

Zhao Qian

Publications and source records attributed to Zhao Qian.

2 recordsLinked to original sources

arXiv2026

Non-Hermitian Complex Coupling for Magnetic Resonance Imaging

Strong coupling in wave-based systems often causes level repulsion, leading to mode splitting and reduced response at the target frequency. This problem is pronounced in magnetic resonance imaging (MRI), where strong mutual inductance between a receive coil (RC) and a metamaterial (MM) degrades B1 performance. Here, we introduce a non-Hermitian complex-coupling decoupling strategy based on a dual-resonator model. By engineering a phase delay in the coupling pathway, an imaginary coupling component is created, driving the system from the PT-symmetric to the anti-PT-symmetric phase and enabling eigenmode degeneracy without added dissipation. Implemented through a high-permittivity ceramic layer, this mechanism restores single-mode resonance in the MM - RC system and suppresses frequency splitting. Simulations show a ~14-fold B1 enhancement compared with the strongly repulsive regime. This passive, compact, and hardware-compatible approach offers a general route for coupling control in electromagnetic, acoustic, optical, and quantum systems.

physics.optics↗

arXiv2024

Gain/Loss-free Non-Hermitian Metamaterials

The ease of using optical gain/loss provides a fertile ground for experimental explorations of non-Hermitian (NH) physics. Without gain/loss, can we realize the NH effect in a Hermitian system? The interface between the coupled Hermitian subsystems is a natural object for NH physics due to the nonconservative process on it. However, it is still far from enduing the interface with rich NH physics. Here, a junction between the topological insulator and the conductor is considered, where the interface can be effectively described by a NH Hamiltonian--such NH character is ascribed to the conductor self-energy of a reservoir. As a consequence of that, we show the wave propagation along the interface exhibits dissipative non-reciprocity (dubbed non-Bloch transport), which was believed to be unique in NH systems. Moreover, the meta-materialization of tight-binding models is also studied by identifying their equivalent connectivity, enabling us to demonstrate the above exotic NH behavior of the interface experimentally. Our work provides a conceptually rich avenue to construct NH systems for both optics and electronics.

physics.optics↗