Exciton-Polariton hybrid skin-topological states

Abstract

The non Hermitian skin effect, where bulk states accumulate at system boundaries, challenges the conventional bulk boundary correspondence. Here we propose a scheme to realize hybrid skin topological states in exciton polariton honeycomb lattices by introducing sublattice dependent gain and loss. This non Hermiticity couples with the intrinsic topological edge modes, leading to relocalization of edge states. We show two distinct regimes: hybrid skin Chern states with switchable localization controlled by TE TM splitting , and hybrid skin antichiral states which preserves the spin polarized property. Our results bridge polariton spin physics and non-Hermitian topology, opening routes toward controllable non reciprocal and spin polarized transport.

Figures (4)

• Figure 1: Schematic figure of the non-Hermitian honeycomb lattice formed by two types of sublattices shown in yellow and blue colors separately. To make the system non-Hermitian, we set sublattice-dependent gain/loss.
• Figure 2: Band structures for Chern insulator $C=2$ (a-b), $C=1$ (c-d) and antichiral edge states (e-f) in non-Hermitian regime. In (a, c, e), the states are color coded according to the imaginary term (gain/loss) and in (b, d, f) are color coded according to the DOCP. In the Chern insulator, the left propagating states and the right propagating states have different signs of imaginary energies and the states are not spin-polarized. For the antichiral case, the edge states are propagating along the same direction and still remain with the spin-polarized properties in the presence of non-Hermiticity. Parameters: $J = 1, z = 0.3J, \gamma_A = -0.05J, \gamma_B = -\gamma_A$. $\delta J = 0.3J$ for (a, b, e, f) and $\delta J = 0.6J$ for (c, d).
• Figure 3: (a,d) Spatial distribution of Hermitian Chern edge states. (b,e) Spatial distribution of the HSCS in two cases. The localization direction can be switched (c,f) Energy spectrum of considered HSCS system for Chern edge states ($C=2,C=1$) separately under both OBCs (color coded according to the expected position) and $x$-PBC/$y$-OBC (black points). Parameters are set the same as in Fig. \ref{['Fig2']}.
• Figure 4: (a,b) Spatial distribution of HSAS, where they are now localized towards left (a) or right (b). (c-d) DOCP of HSAS; upper edge is spin "-" and lower edge is spin "+". (e) Energy spectrum of the considered HSAS system under both OBCs (color coded according to the expected position) and $x$-PBC/$y$-OBC (black points). (f) Energies from both OBCs are color coded according to the DOCP.