BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Mário Silveirinha (Instituto Superior Técnico) DTSTART:20200624T100000Z DTEND:20200624T110000Z DTSTAMP:20260423T024701Z UID:QM3/6 DESCRIPTION:Title: Topo logical theory of non-Hermitian photonic systems\nby Mário Silveirinh a (Instituto Superior Técnico) as part of Quantum Matter meets Maths (IST \, Lisbon)\n\n\nAbstract\nRecently\, topological materials and topological effects have elicited a great interest in the photonics community [1]. W hile condensed-matter phenomena are traditionally described by Hermitian o perators\, the same is not true in the context of macroscopic electrodynam ics where a dissipative response is the rule\, not the exception. In this talk\, I will discuss how to determine the topological phases of dissipati ve (non-Hermitian) photonic structures from first principles using a gauge -independent Green function [2\, 3]. It is shown that analogous to the Her mitian case\, the Chern number can be expressed as an integral of the syst em Green function over a line parallel to the imaginary-frequency axis. Th e approach introduces in a natural way the "band-gaps" of non-Hermitian sy stems as the strips of the complex-frequency plane wherein the system Gree n function is analytical. I apply the developed theory to nonreciprocal el ectromagnetic continua and photonic crystals\, with lossy and or gainy ele ments. Furthermore\, I discuss the validity of the bulk-edge correspondenc e in the non-Hermitian case.\n\n[1] L. Lu\, J. D. Joannopoulos\, M. Solja čić\, "Topological photonics"\, Nat. Photonics\, 8\, 821\, (2014).\n\n[2 ] M. G. Silveirinha\, "Topological theory of non-Hermitian photonic system s"\, Phys. Rev. B\, 99\, 125155\, 2019.\n\n[3] F. R. Prudêncio\, M. G. Si lveirinha\, First Principles Calculation of Topological Invariants of non- Hermitian Photonic Crystals\, arXiv:2003.01539\n LOCATION:https://researchseminars.org/talk/QM3/6/ END:VEVENT END:VCALENDAR