21 October

Topological photonics: mistaken paradigms and new opportunities

Monday 21 October 2019, 03:00pm

ICN2 Seminar Hall, ICN2 Building, UAB

Dr Aitzol Gacía-Etxarri, Donostia International Physics Center, San Sebastián, Spain / IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

Hosted by: Prof. Clivia M. Sotomayor, Phononic and Photonic Nanostructures Group Leader at ICN2

Abstract: Topological states of matter were first discovered in the field of solid-state physics but recent contributions are proving their existence in diverse fields of science. To mention a few, topological surface states have been recently identified in the fields of optics [1], acoustics [2] and in excitonic and polaritonic materials [3].

Most of these cross-disciplinary designs have been directly inherited from concepts previously discovered in electronic materials. Nevertheless, these different physical mechanisms, should lead to distinct effects with interesting properties of their own. Unfortunately those assets will remain hindered if the research on topological effects in these fields continues to be exclusively based on analogies with solid-state systems.

A recent article unveiled a new method, named Topological Quantum Chemistry (TQC) [4], which allows predicting the emergence of topological phases on matter based exclusively on Elementary Band Representations, a mathematical tool very well known in the field of crystallography. Applying TQC to electronic, photonic, excitonic and acoustic systems could unveil the emergence of novel and distinct topological states pivoted by the unique characteristics of the distinct physical excitations in each system.

In this work, we applied TQC to Photonic crystals; surprisingly, we discovered that certain paradigms in the design of Photonic Topological insulators are not strictly truthful. Moreover, the versatility of the method allowed us to design novel topological photonic systems with unprecedented physical properties. In particular, we will introduce the first instance of fragile topology in a physical system. 

[1] Lu, L., et. al. Nature Photonics, 8(11), 821 (2014)

[2] He, Cheng, et. al. Nature Physics, vol. 12, no 12, p. 1124 (2016)

[3] S. Klemb et. al. Nature 562, 552–556 (2018)

[4] Barry Bradlyn et. Al. Nature 547 (7663), 298 (2017)

[5] M. Blanco de Paz et. al. arXiv:1903.02562 [cond-mat.mes-hall] (2019)