Seminarium Fizyki Ciała Stałego

In quantum mechanics, the assumed hermicity of the Hamiltonian ensures that the probability of finding a particle is constant over time. The description of dissipation or gain in a system typically requires introduction of non-Hermitian terms. The resulting non-Hermitian Hamiltonian can exhibit properties unavailable for typical Hermitian systems. The most striking example of such behavior is the existence of so-called Exceptional Points (EP), points in parameter space where both eigenvalues and eigenvectors coalesce (are degenerate).In this work, we introduce the basics of non-Hermitian physics with special emphasis on the properties of EPs. Specifically, we consider a planar optical microcavity filled with a birefringent liquid crystal. We show how polarization dependent losses in such a system lead to emergence of EPs. We demonstrate, both theoretically and experimentally, how owing to the sensibility of the liquid crystal to an external electric field, it is possible to change the position of the EPs. In particular, we show how EPs can be removed (annihilated) from the system when two of them are brought into a single position.M. Król, I. Septembre et al., Annihilation of exceptional points from different Dirac valleys in a 2D photonic system, Nat. Commun. 13, 5340 (2022).UwagaSeminarium w trybie HybrydowymFaculty of Physics room 0.06link to remote mode:https://zoom.us/j/7218838148szczegóły patrz instrukcja :instrukcja: (pdf file)AttentionThe seminar in the Hybrid modeFaculty of Physics room 0.06for details see instruction :instruction: (pdf file)