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Title: Photonic topological insulator with broken time-reversal symmetry

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$$2\atop{f}$$ = -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$$2\atop{b}$$ = -1. Here, 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$$2\atop{p}$$ = -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.
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [2]
  1. Nanjing Univ. (China). National Lab. of Solid State Microstructures and Dept. of Materials Science and Engineering
  2. Nanjing Univ. (China). Collaborative Innovation Center of Advanced Microstructures (CICAM), National Lab. of Solid State Microstructures and Dept. of Materials Science and Engineering
  3. Univ. of Oxford (United Kingdom). Clarendon Lab. and Dept. of Physics
  4. State Univ. of New York (SUNY), Buffalo, NY (United States). Dept. of Electrical Engineering
Publication Date:
Grant/Contract Number:
SC0014485; 2012CB921503; 2013CB632702; 11134006; 11474158; 11404164; 187 N66001-11-1-4105
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 18; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
State Univ. of New York (SUNY), Buffalo, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Basic Research Program of China; National Nature Science Foundation of China (NSFC); Defense Advanced Research Projects Agency (DARPA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; photonic topological insulator; piezoelectric/piezomagnetic superlattice; photonic crystal; polariton; time-reversal symmetry
OSTI Identifier:
1469298

He, Cheng, Sun, Xiao-Chen, Liu, Xiao-Ping, Lu, Ming-Hui, Chen, Yulin, Feng, Liang, and Chen, Yan-Feng. Photonic topological insulator with broken time-reversal symmetry. United States: N. p., Web. doi:10.1073/pnas.1525502113.
He, Cheng, Sun, Xiao-Chen, Liu, Xiao-Ping, Lu, Ming-Hui, Chen, Yulin, Feng, Liang, & Chen, Yan-Feng. Photonic topological insulator with broken time-reversal symmetry. United States. doi:10.1073/pnas.1525502113.
He, Cheng, Sun, Xiao-Chen, Liu, Xiao-Ping, Lu, Ming-Hui, Chen, Yulin, Feng, Liang, and Chen, Yan-Feng. 2016. "Photonic topological insulator with broken time-reversal symmetry". United States. doi:10.1073/pnas.1525502113. https://www.osti.gov/servlets/purl/1469298.
@article{osti_1469298,
title = {Photonic topological insulator with broken time-reversal symmetry},
author = {He, Cheng and Sun, Xiao-Chen and Liu, Xiao-Ping and Lu, Ming-Hui and Chen, Yulin and Feng, Liang and Chen, Yan-Feng},
abstractNote = {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$2\atop{f}$ = -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$2\atop{b}$ = -1. Here, 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, Tp (T$2\atop{p}$ = -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 Tp rather than by the bosonic time-reversal symmetry Tb. 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.},
doi = {10.1073/pnas.1525502113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 18,
volume = 113,
place = {United States},
year = {2016},
month = {4}
}