Non-Hermitian Complex Coupling for Magnetic Resonance Imaging

TL;DR

This paper introduces a non-Hermitian complex-coupling method to control mode interactions in MRI systems, significantly improving B1 field strength by restoring single-mode resonance through engineered phase delays.

Contribution

It presents a novel non-Hermitian coupling strategy that enables eigenmode degeneracy without dissipation, enhancing MRI performance.

Findings

Achieved approximately 14-fold B1 enhancement in simulations

Restored single-mode resonance by suppressing frequency splitting

Demonstrated a passive, hardware-compatible coupling control method

Abstract

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.