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Annihilation of exceptional points from different Dirac valleys in a 2D photonic system by Król, M.; Septembre, I.; Oliwa, P.; Kędziora, M.; Łempicka-Mirek, K.; Muszyński, M.; Mazur, R.; Morawiak, P.; Piecek, W.; Kula, P.; Bardyszewski, W.; Lagoudakis, P. G.; Solnyshkov, D. D.; Malpuech, G.; Piętka, B.; Szczytko, J. is a scholarly article available to read on EtoBox.

What is Annihilation of exceptional points from different Dirac valleys in a 2D photonic system about?

Topological physics relies on the existence of Hamiltonian's eigenstate singularities carrying a topological charge, such as quantum vortices, Dirac points, Weyl points and -- in non-Hermitian systems -- exceptional points (EPs), lines or surfaces. They appear only in pairs connected by a Fermi arc and are related to a Hermitian singularity, such as a Dirac point. The annihilation of 2D Dirac points carrying opposite charges has been experimentally reported. It remained elusive for Weyl points and second order EPs terminating different Fermi arcs. Here, we observe the annihilation of second order EPs issued from different Dirac points forming distinct valleys. We study a liquid crystal microcavity with voltage-controlled birefringence and TE-TM photonic spin-orbit-coupling. Two neighboring modes can be described by a two-band Hermitian Hamiltonian showing two topological phases with either two same-sign or four opposite-sign Dirac points (valleys). Non-Hermiticity is provided by polarization-dependent losses, which split Dirac points into pairs of EPs, connected by Fermi arcs. We measure their topological charges and control their displacement in reciprocal space by increasing the

Author

Król, M.; Septembre, I.; Oliwa, P.; Kędziora, M.; Łempicka-Mirek, K.; Muszyński, M.; Mazur, R.; Morawiak, P.; Piecek, W.; Kula, P.; Bardyszewski, W.; Lagoudakis, P. G.; Solnyshkov, D. D.; Malpuech, G.; Piętka, B.; Szczytko, J.

Published

2021

Language

EN