# Polariton condensation in photonic crystals with high molecular orientation

## TL;DR

This paper demonstrates the formation of exciton-polariton Bose-Einstein condensates in a two-dimensional photonic crystal with an organic semiconductor, highlighting the effects of photon momentum and detuning on condensation.

## Contribution

It presents the first analysis of polariton condensation in a defect-free photonic crystal with high molecular orientation, including non-zero momentum states and threshold control.

## Key findings

- Condensation occurs at points where photon group velocity is zero.
- Condensation at non-zero momentum states is achievable with incoherent pumping.
- Condensation thresholds depend on detuning and reciprocal space points.

## Abstract

We study Frenkel exciton-polariton Bose-Einstein condensation in a two-dimensional defect-free triangular photonic crystal with an organic semiconductor active medium containing bound excitons with dipole moments oriented perpendicular to the layers. We find photonic Bloch modes of the structure and consider their strong coupling regime with the excitonic component. Using the Gross- Pitaevskii equation for exciton polaritons and the Boltzmann equation for the external exciton reservoir, we demonstrate the formation of condensate at the points in reciprocal space where photon group velocity equals zero. Further, we demonstrate condensation at non-zero momentum states for TM-polarized photons in the case of a system with incoherent pumping, and show that the condensation threshold varies for different points in the reciprocal space, controlled by detuning.