近日，新西兰奥塔哥大学N. J. Lambert团队实现了利用异常点对磁非极化子进行相干控制。该项研究成果发表在2025年8月19日出版的《自然—物理学》杂志上。

在非厄米系统中，谐振振荡的振幅随时间增长或衰减，对应于具有增益或损耗的模态。当两个耦合模具有特定的增益-损失不平衡时，系统的本征频率和本征模会在一个特殊点上合并。特殊点由于其拓扑性质对系统的动力学具有定性影响，并且已经以控制系统为主题，包括光学微腔，奇偶时间对称波导的激光和太赫兹脉冲的产生。一个具有挑战性的开放问题是在与激励的相干控制相关的时间尺度上对系统损失和增益的完全确定性和直接操纵。

研究组展示了对磁非极化子复频率的快速操纵，其持续时间远短于其衰变速率，使它们能够利用非厄米物理进行相干控制。通过动态环绕一个异常点，研究组证明了耦合磁非极化模式之间的数量转移。然后，他们直接通过一个异常点驱动系统，并证明这允许在本征模的相等叠加中制备耦合系统。这些发现为探索非厄米系统的丰富动力学性质建立了一个高度可控的混合平台。

附：英文原文

Title: Coherent control of magnon–polaritons using an exceptional point

Author: Lambert, N. J., Longdell, J. J., Schwefel, H. G. L., Schumer, A., Rotter, S.

Issue&Volume: 2025-08-19

Abstract: In a non-Hermitian system, the amplitude of resonant oscillations can either grow or decay in time, corresponding to a mode with either gain or loss. When two coupled modes have a specific gain–loss imbalance, an exceptional point emerges at which both eigenfrequencies and eigenmodes of the system coalesce. Exceptional points have qualitative effects on the dynamics of systems due to their topological properties, and have been used to control systems including optical microcavities, the lasing of a parity–time-symmetric waveguide and terahertz pulse generation. A challenging open problem is the fully deterministic and direct manipulation of the systems’ loss and gain on timescales relevant to the coherent control of excitations. Here we demonstrate the rapid manipulation of the complex frequency of magnon–polaritons on durations much shorter than their decay rate, allowing us to exploit non-Hermitian physics for coherent control. By dynamically encircling an exceptional point, we demonstrate population transfer between coupled magnon–polariton modes. We then drive the system directly through an exceptional point, and demonstrate that this allows the coupled system to be prepared in an equal superposition of eigenmodes. These findings establish a highly controllable hybrid platform for exploring the rich dynamical properties of non-Hermitian systems.

DOI: 10.1038/s41567-025-02998-3

Source: https://www.nature.com/articles/s41567-025-02998-3