One-dimensional ZnO exciton polaritons with negligible thermal broadening at room temperature

Phonon damping is the main source of pure dephasing in the solid state, limiting many fundamental quantum effects to low temperature observations. Here we show how excitons in semiconductors can be totally decoupled from the phonon bath, even at room temperature, thanks to their strong interaction with photons. To do so, we investigated ZnO microwires, a new semiconductor nanostructure made of large band-gap material where the light can be trapped and guided into whispering gallery modes. In this system, the very large coupling regime between exciton and photon results in unusual exciton-polariton of one-dimensional character and Rabi splitting as large as 300meV. We find that polariton modes of excitonic fraction up to 75% exhibit no thermal broadening up to room temperature. We show that this remarkable behavior is due to the very large Rabi splitting as compared to the LO phonon energy.