Abstract
Floquet topological systems exhibit rich physics associated with quasienergy band structures and new topological states; nevertheless, they are usually explored in Hermitian systems. Recent studies have shown the capability of non-Hermiticity in engineering topological states, while the interplay of Floquet topological phases and non-Hermiticity remains unclear. Here, we reveal that the non-Hermitian modulation can induce the phase transitions between trivial and nontrivial topological Floquet states. Our study theoretically predicts that the non-Hermitian modulation can create a Floquet π mode in an originally topological trivial system according to the reopening of quasienergy band gap (i.e., the π gap), which is well confirmed experimentally in the silicon waveguide platform. Our approach shows the powerful capability of non-Hermitian modulation in engineering topological modes in Floquet photonics systems and would inspire different possibilities in optical field manipulation in open systems.1 MoreReceived 8 February 2021Revised 31 March 2021Accepted 28 April 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023211Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEdge statesTopological phase transitionPhysical SystemsWaveguide arraysPropertiesPT-symmetryCondensed Matter, Materials & Applied Physics
Highlights
Floquet topological systems exhibit rich physics associated with quasienergy band structures and new topological states; they are usually explored in Hermitian systems
There have been a lot of works about topological protected photonic modes realized in various systems
Topological photonic configurations have been extended from static to periodically driven systems, known as Floquet topological photonics (FTP) [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]
Summary
Floquet topological systems exhibit rich physics associated with quasienergy band structures and new topological states; they are usually explored in Hermitian systems. Non-Hermitian systems with parity-time (PT) symmetry modulation have received great attention in the photonics, in which gain and loss can be introduced to control optical modes and light propagations [31,32,33,34,35,36,37,38,39,40].
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