论文标题
全磁性结构中的高阶特殊点
Higher-order exceptional points in all-magnetic structures
论文作者
论文摘要
在解决各种物理和工程问题时，高度要求具有特殊灵敏度的磁力计，例如测量地球弱磁场以及勘探矿物沉积物和地质结构。已经表明，由于对外部扰动的非线性响应，在特殊点（EPS）处的非热堕落性（EPS）可以为此目的提供新的途径。最近的一项工作[H. Yang等人，物理。莱特牧师。 121，197201（2018）]已迈出了第一步，以实现尊重平等时间对称性的铁手令双层中的二阶Magnonic EP。在本文中，我们通过考虑由增益，中性和（平衡 - ）损耗层组成的铁磁三层人士来概括为高阶案例。我们通过调整层间耦合强度，外部磁场和增益损失参数来观察二阶和三阶横杆菌EPS。我们表明，与常规的磁性隧道连接器相比，可以通过$ 3 $的数量级来增强磁灵敏度。我们的结果为研究纯磁系统中的高阶EPS和设计具有超高灵敏度的磁性传感器的方式铺平了道路。
Magnetometers with exceptional sensitivity are highly demanded in solving a variety of physical and engineering problems, such as measuring Earth's weak magnetic fields and prospecting mineral deposits and geological structures. It has been shown that the non-Hermitian degeneracy at exceptional points (EPs) can provide a new route for that purpose, because of the nonlinear response to external perturbations. One recent work [H. Yang et al., Phys. Rev. Lett. 121, 197201 (2018)] has made the first step to realize the second-order magnonic EP in ferromangetic bilayers respecting the parity-time symmetry. In this paper, we generalize the idea to higher-order cases by considering ferromagnetic trilayers consisting of a gain, a neutral, and a (balanced-)loss layer. We observe both second- and third-order magnonic EPs by tuning the interlayer coupling strength, the external magnetic field, and the gain-loss parameter. We show that the magnetic sensitivity can be enhanced by $3$ orders of magnitude comparing to the conventional magnetic tunneling junction based sensors. Our results pave the way for studying high-order EPs in purely magnetic system and for designing magnetic sensors with ultrahigh sensitivity.
