XXXVI Reunión Bienal de la Real Sociedad Española de Física

Temperature dependence of the coherence in polariton condensates

Not scheduled

Aula Magna (Santiago de Compostela, Facultade de Química)

Quantum Materials and Technologies (GEFES)

Description

In this work, we investigate the temperature dependence of the degree of coherence of traveling polariton condensates. Coherence is a key factor in condensates and, as a consequence of the wave-particle behavior of polaritons, it is possible to study the coherence just by measuring interferences between condensates using spectroscopic techniques. A recent study of Antón et al. showed the presence of interference fringes in momentum (k) space produced by the phase correlation between two polariton condensates [1]. Since the condensates were separated by 70 µm, these experiments proved the existence of remote coherence between them. Here, we study the thermal robustness of this coherence. The sample used in this work consists of a high-quality GaAs-based 1D-microcavity, surrounded by two Bragg mirrors, with ridge structures sculpted on it. We excite the sample with two, spatially separated, pulsed-laser beams. The time-resolved emission is analyzed both in real- and momentum-space, where we perform a detailed Fourier analysis of the interference patterns to study the coherence. We focus our attention on three time delays of particular interest (Fig.1): at t = 0 in k-space, when the condensates start moving and acquire a maximum momentum; at t = 30 ps, when the two components of the condensate meet in real-space, and at t = 55 ps in k-space, when they stop at the potential barriers created by photo-created excitons, joining at k = 0. Our measurements show the existence of an exponential loss of coherence with increasing temperature both in real- and k-space. [1] C. Antón, G. Tosi, M. D. Martín, Z. Hatzopoulos, G. Konstantinidis, P. S. Eldridge, P. G. Savvidis, C. Tejedor, L. Viña, Phys. Rev. B 90 (2014) 081407