Yang Y, Wang Yi-Pu, Rao J W, Gui Y S, Yao B M, Lu W, Hu C-M
Department of Physics and Astronomy, University of Manitoba, Winnipeg R3T 2N2, Canada.
State Key Laboratory of Infrared Physics, Chinese Academy of Sciences, Shanghai 200083, People's Republic of China.
Phys Rev Lett. 2020 Oct 2;125(14):147202. doi: 10.1103/PhysRevLett.125.147202.
By engineering an anti-parity-time (anti-PT) symmetric cavity magnonics system with precise eigenspace controllability, we observe two different singularities in the same system. One type of singularity, the exceptional point (EP), is produced by tuning the magnon damping. Between two EPs, the maximal coherent superposition of photon and magnon states is robustly sustained by the preserved anti-PT symmetry. The other type of singularity, arising from the dissipative coupling of two antiresonances, is an unconventional bound state in the continuum (BIC). At the settings of BICs, the coupled system exhibits infinite discontinuities in the group delay. We find that both singularities coexist at the equator of the Bloch sphere, which reveals a unique hybrid state that simultaneously exhibits the maximal coherent superposition and slow light capability.
通过构建一个具有精确本征空间可控性的反宇称时间（anti-PT）对称腔磁振子系统，我们在同一系统中观测到了两种不同的奇点。一种奇点类型是例外点（EP），它是通过调节磁振子阻尼产生的。在两个例外点之间，光子和磁振子态的最大相干叠加由保留的反PT对称性稳健地维持。另一种奇点类型源于两个反共振的耗散耦合，是一种非常规的连续谱束缚态（BIC）。在连续谱束缚态的设置下，耦合系统在群延迟中表现出无限不连续性。我们发现这两种奇点在布洛赫球的赤道处共存，这揭示了一种独特的混合态，它同时展现出最大相干叠加和慢光能力。
