Institut des
NanoSciences de Paris
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Séminaire général

Ultra-cold Indirect Excitons

François Dubin

In this presentation, I will detail recent experimental studies addressing a possible Bose-Einstein condensation of semiconductor excitons. In particular, I will emphasize spatially indirect excitons which are engineered by spatially separating electrons and holes. On the first hand, I will discuss a situation for which indirect excitons are created by combined optical and electrical injection of electronic carriers. I will show that peculiar spatial patterns arise in this regime, and particularly macroscopic ring-shaped structures. Strikingly, exciton rings undergo a spatial fragmentation as temperature is lowered and at the same time a spin pattern is spontaneously established. The manifestation of the excitons quantum condensation in these experiments will then be discussed. On the other hand, I will show that one can exploit the large and well oriented electric dipole characteristic of indirect excitons in order to create exciton traps and even circuits. In particular, I will report an all-optical approach that allows us to program on-demand and in-situ the confinement landscape of indirect excitons. As shown by pioneering studies realized with atomic vapors, this degree of control offers a promising route to deterministically engineer collective quantum phenomena with ultra-cold indirect excitons.