Origin of robust exceptional points: Restricted bulk zero mode
Origin of robust exceptional points: Restricted bulk zero mode
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DOI：
10.1103/physreva.101.063823
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发表时间：
2020-05
影响因子：
2.9
通讯作者：
J. H. Rivero;L. Ge
中科院分区：
文献类型：
--
作者：
J. H. Rivero;L. Ge
最近发现了一种对体相耦合无序不敏感的鲁棒例外点。在这里，我们表明，出现的差距时，在这个一维阵列中的耦合光学腔的数量从偶数到奇数的变化。鲁棒例外点只存在于前一种情况下，而在后一种情况下，例外点所需的耦合与腔阵列的大小成反比，并且在体中受到耦合无序的影响。我们进一步证明了这两种情况下的例外点分别是二阶和三阶的。我们阐明了作为一个受限制的体零模式，它共享相同的鲁棒性对耦合无序和具有有限的振幅相邻的边界的强大EP的起源。这一发现使我们能够可靠地识别出高维系统中的鲁棒EP，这些EP可以存在于亚晶格对称性或从其演化而来的非厄米粒子-空穴对称性的存在下。
Recently a type of robust exceptional point was found that is insensitive to the coupling disorder in the bulk. Here we show that a disparity emerges when the number of coupled optical cavities in this one-dimensional array changes from even to odd. The robust exceptional point only exists in the former case, whereas in the latter the required coupling for the exceptional point depends inversely on the size of the cavity array and is subjected to coupling disorder in the bulk. We further show that the exceptional points in these two cases are second and third order, respectively. We elucidate the origin of the robust EP as a restricted bulk zero mode, which shares the same robustness against coupling disorder and has a finite amplitude adjacent to the boundary. This finding enables us to identify robust EPs in higher-dimensional systems reliably, which can exist in the presence of either sublattice symmetry or the non-Hermitian particle-hole symmetry evolved from it.