Seminar on "Non-Hermitian trapping of Dirac polariton condensates" by Dr. Anton Nalitov

On Wednesday, November 6 at 11.00, Moscow time, ACTP will hold the seminar on "Non-Hermitian trapping of Dirac polariton condensates" by Dr. Anton Nalitov (ACTP, Moscow Institute of Physics and Technology).
В среду, 6 ноября в 11.00, состоится семинар, на котором будет заслушан доклад д. ф.-м. н. Антона Налитова (Международный Центр Теоретической Физики им. А.А. Абрикосова, МФТИ) "Неэрмитовая модель локализации дираковских поляритонных конденсатов".
Abstract
The perfect transparency of any potential barrier for ultra-relativistic massless Dirac particles is, perhaps, the most vivid illustration of the famous Klein paradox. As a consequence, forbidden reflection obstructs confinement of such a particle, as it can always escape any potential trap in a form of an anti-particle. Although for massive Dirac particles, characterized with a gap in energy dispersion between the particle and the anti-particle branches, partial reflection is allowed, confinement is still suppressed due to the intrinsic particle-hole symmetry.
Exciton-polaritons, light-matter quasi-particles emerging from the strong coupling of excitons and photons, can mimic ultra-relativistic behavior and Klein paradox when placed in photonic crystals. However, having finite lifetimes limited by hundreds of picoseconds on one hand and experiencing gain due to bosonic stimulated scattering on the other, polaritons are described with open driven-dissipative models. In particular, non-Hermitian description captures major spectral and dynamical properties of Dirac polariton condensates in photonics crystals supporting states bound in the continuum, including nonequilibrium bosonic condensation.
We demonstrate that, in stark contrast with the conservative case, nonequilibrium bosonic condensates of Dirac polaritons can be trapped with effective non-Hermitian potentials even in the absence of an energy gap, associated with emergent mass. Effective confinement is revealed in observed size quantization of polariton emission under nonresonant optical excitation focused onto a few-micron pumping spot. Spectral quantization, specific shaping of polariton emission in real and reciprocal space, and dependence of polariton emission on the pumping power, are reproduced with the non-Hermitian two-component model.