Photonic topological insulator with broken time-reversal symmetry
Photonic topological insulator with broken time-reversal symmetry
复制标题
具有破缺时间反转对称性的光子拓扑绝缘体
DOI：
10.1073/pnas.1525502113
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发表时间：
2016-05-03
影响因子：
11.1
通讯作者：
Chen, Yan-Feng
中科院分区：
文献类型：
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作者：
He, Cheng;Sun, Xiao-Chen;Chen, Yan-Feng
拓扑绝缘体是一种内部绝缘，但边缘态受时间反转保护的材料。自从近十年前预测和发现以来，这种受保护的拓扑相已经在光子学领域的电子系统之外进行了探索。电子是自旋1/2的粒子，而光子是自旋1的粒子。这两种粒子之间的自旋差异意味着它们对应的对称性根本不同。众所周知，电子拓扑绝缘体受到电子自旋-1/2（费米子）时间反演对称性T-f（2）=-1的保护。然而，由于光子自旋为1（玻色子）的时间反演对称性T-b（2）= 1，在正常情况下光子拓扑绝缘体不存在相同的保护。在这项工作中，我们报告了一个光子拓扑绝缘体的设计使用Tellegen磁电耦合作为光子赝自旋轨道相互作用的左，右圆极化螺旋自旋态。Tellegen磁电耦合破坏了玻色子时间反演对称性，但由于电磁对偶性，反而产生了保守的人工类费米子伪时间反演对称性T-p（T-p（2）= -1）。令人惊讶的是，我们发现，在这个系统中，螺旋边缘的状态，事实上，保护这种费米类伪时间反演对称性Tp，而不是玻色子时间反演对称性Tb。这一显著的发现有望为理解其他基本粒子拓扑相的对称性保护机制以及寻找拓扑绝缘体的新实现铺平新的道路。
A topological insulator is a material with an insulating interior but time-reversal symmetry-protected conducting edge states. Since its prediction and discovery almost a decade ago, such a symmetry-protected topological phase has been explored beyond electronic systems in the realm of photonics. Electrons are spin-1/2 particles, whereas photons are spin-1 particles. The distinct spin difference between these two kinds of particles means that their corresponding symmetry is fundamentally different. It is well understood that an electronic topological insulator is protected by the electron's spin-1/2 (fermionic) time-reversal symmetry T-f(2) = -1. However, the same protection does not exist under normal circumstances for a photonic topological insulator, due to photon's spin-1 (bosonic) time-reversal symmetry T-b(2) = 1. In this work, we report a design of photonic topological insulator using the Tellegen magnetoelectric coupling as the photonic pseudospin orbit interaction for left and right circularly polarized helical spin states. The Tellegen magnetoelectric coupling breaks bosonic time-reversal symmetry but instead gives rise to a conserved artificial fermionic-like-pseudo time-reversal symmetry, T-p (T-p(2) = -1), due to the electromagnetic duality. Surprisingly, we find that, in this system, the helical edge states are, in fact, protected by this fermionic-like pseudo time-reversal symmetry T-p rather than by the bosonic time-reversal symmetry T-b. This remarkable finding is expected to pave a new path to understanding the symmetry protection mechanism for topological phases of other fundamental particles and to searching for novel implementations for topological insulators.