Coupling between Exciton-Polariton Corner Modes through Edge States

Abstract

Recently realized higher order topological insulators have taken a surge of interest among the theoretical and experimental condensed matter community. The two dimensional second order topological insulators give rise to zero dimensional localized corner modes that reside within the band gap of the system along with edge modes that inhabit a band edge next to bulk modes. Thanks to the topological nature, information can be trapped at the corners of these systems which will be unhampered even in the presence of disorder. Being localized at the corners, the exchange of information among the corner states is an issue. Here we show that the nonlinearity in an exciton polariton system can allow the coupling between the different corners through the edge states based on optical parametric scattering, realizing a system of multiple connectible topological modes.

Higher-order quantum spin Hall effect in a photonic crystal

“…These lowerdimensional boundary states such as hinge states and corner states provide new degrees of freedom with which to manipulate waves and support integrated topological devices. Previous experimental realizations of HOTIs were all limited to explorations of the existence and robustness of these boundary states [27][28][29][30][31][32][33][34][35][36][37] . The internal degrees of freedom of waves, such as the spin and pseudospin, offer a new dimension with which to investigate the wave physics and sustain vast applications from the information processing to the topological quantum computing which have so far not been intertwined with the higher-order topology.…”

Synthetic band-structure engineering in polariton crystals with non-Hermitian topological phases

“…( 6 ) in ‘Methods’), but their conjugate is not taken in the lower off-diagonal element of the above Hamiltonian. This is due to the non-Hermitian nature of our system, which, in the context of topologically nontrivial phases, has taken a surge of interest 19 – 21 , 55 – 61 . In a ring-shaped lattice that forms periodic boundary conditions that we discuss later, the Bloch waves are exact eigenstates and the description of the Zak phase also becomes exact.…”

Optical switching of topological phase in a perovskite polariton lattice

“…Recently, microcavity exciton polariton systems have emerged as a unique platform for topological photonics (11,12,(28)(29)(30)(31)(32)(33)(34), representing a linking bridge between photonics and condensed matter. Exciton polaritons are half-light, half-matter quasiparticles, which result from the strong coupling between cavity photons and excitons.…”

“…Here, we demonstrate an exciton polariton topological insulator with polarization-dependent phases in a one-dimensional (1D) perovskite lattice at room temperature, which is based on the Su-Schrieffer-Heeger (SSH) model by coupling the s-orbital type polariton modes with a zigzag chain of nanopillars. By using the anisotropy and strong photonic spin-orbit coupling from the halide perovskite microcavity (36,40,41), we demonstrate the emergence of topological polariton edge states locating inside a large topological gap of ~10 meV, which is essential for nonlinear devices that seek to use energy shifts to realize switches and information processing while remaining topological (32). In the meantime, it allows distinct topological phase switching between topologically nontrivial phase and topologically trivial phase by means of polarization switching.…”