Title: Quantum Geometry and Magneto-optical Effects in Plasmonic Lattices
When: Tuesday, 21th November, 2023, at 12:00.
Where: Department of Theoretical Condensed Matter Physics, Faculty of Sciences, Module 5, Seminar Room (5th Floor).
Speaker: Javier Cuerda, Department of Applied Physics, Aalto University School of Science, Aalto FI-00076, Finland.
Plasmonic nanoparticles arranged in two-dimensional lattices enable strong light-matter coupling, lasing, and Bose-Einstein condensation [1, 2], and hold intriguing prospects for topological photonics and related applications, such as extremely robust signal processing through topological protection against imperfections, or unidirectional propagation of optical modes [3, 4]. These so-called plasmonic lattices sustain electromagnetic modes named surface lattice resonances (SLRs) that emerge from the long-range radiative interactions provided by the diffraction orders of the lattice, which mediate between the localized resonances of individual nanoparticles. The description of SLRs goes well beyond tight binding approximations, opening an intriguing new regime for studies on topological photonics.
In this talk, I will show how the long range, polarization-dependent coupling between nanoparticles, in combination with time-reversal symmetry breaking, enable a plethora of new phenomena. We have demonstrated that the inherently weak effects of magnetic time-reversal symmetry breaking in plasmonics become prominent in the lasing regime through suitable mode design, leading to active control and full on–off switching of the lasing signal from a lattice of Co/Pt multilayer nanoparticles immersed in an IR-140 dye solution . In addition, we have experimentally observed non-zero quantum metric and Berry curvature along the diagonals of the Brillouin zone of a square lattice of gold nanoparticles . By a theoretical analysis, we showed that the Berry curvature originates solely from non-Hermitian effects . Our results inspire new pathways in the design of topological systems by tailoring losses or gain, and introduce magnetization as a novel mechanism to control nanoscale lasers.
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