Leykam Daniel, Bliokh Konstantin Y, Huang Chunli, Chong Y D, Nori Franco
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
CEMS, RIKEN, Wako-shi, Saitama 351-0198, Japan.
Phys Rev Lett. 2017 Jan 27;118(4):040401. doi: 10.1103/PhysRevLett.118.040401. Epub 2017 Jan 23.
We analyze chiral topological edge modes in a non-Hermitian variant of the 2D Dirac equation. Such modes appear at interfaces between media with different "masses" and/or signs of the "non-Hermitian charge." The existence of these edge modes is intimately related to exceptional points of the bulk Hamiltonians, i.e., degeneracies in the bulk spectra of the media. We find that the topological edge modes can be divided into three families ("Hermitian-like," "non-Hermitian," and "mixed"); these are characterized by two winding numbers, describing two distinct kinds of half-integer charges carried by the exceptional points. We show that all the above types of topological edge modes can be realized in honeycomb lattices of ring resonators with asymmetric or gain-loss couplings.
我们分析二维狄拉克方程非厄米变体中的手性拓扑边缘模式。此类模式出现在具有不同“质量”和/或“非厄米电荷”符号的介质之间的界面处。这些边缘模式的存在与体哈密顿量的例外点密切相关，即介质体谱中的简并。我们发现拓扑边缘模式可分为三个族（“类厄米”、“非厄米”和“混合”）；它们由两个缠绕数表征，描述了例外点所携带的两种不同的半整数电荷。我们表明，上述所有类型的拓扑边缘模式都可以在具有不对称或增益 - 损耗耦合的环形谐振器蜂窝晶格中实现。
