Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 37: Cold Atomic Gases

TT 37.1: Hauptvortrag

Dienstag, 1. April 2014, 09:30–10:00, HSZ 304

Superfluidity and Collective Pairing in Polariton Microcavities — •Francesca Maria Marchetti — Departamento de Fisica Teorica de la Materia Condensada & IFIMAC, Universidad Autonoma de Madrid, Madrid 28049, Spain

Matter-light systems such as semiconductor microcavities have been witnessing remarkable advances, promoting them as ideal environments where to engineer and study novel collective quantum states. Since the first realisation of a polariton Bose-Einstein condensate, the field has grown at a high rate. Superfluid behaviour, the observation of full and half quantum vortices and solitons, the optical spin Hall effect, are just few examples of the most seminal results for polaritonic fluids obtained only in the last few years, a brief account of which will be given in the introduction of this presentation. Most recently, it has been possible to tune the interaction strength between polaritons with opposite polarisations via a bipolariton Feshbach resonance mechanism. This allows to access regimes of tunable pairing and strong correlations, opening a wealth of interesting possibilities. I will in particular show that microcavity polaritons present an ideal opportunity to study bosonic collective pairing phases: Exploring the theoretical phase diagram, I will show that, by using the photon-exciton detuning as the interaction tuning parameter, a novel phase transition between the regular polariton superfluid phase and a ``molecular'' (i.e. bipolariton) superfluid phase can be realised. Temperatures and detunings required for typical materials such as GaAs and ZnO are attainable, and I will discuss experimental signatures for detecting such novel phases.