Exciton-polariton condensates in acoustic periodic potentials.

• Applicant: Dr. Paulo V. Santos, since 9/2015
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 221587993

Macroscopic quantum phases - fundamental collective states of matter described by a single wavefunction - have always attracted an intense research interest. A well-known example are Bose-Einstein condensates (BEC) in atomic systems, whose properties have been studied using magnetic and optical fields. Periodic lattices formed by interference of laser beams are a particularly succesful tool for modulation of BECs. Its use has derived in new concepts for manipulation of quantum states useful for fundamental studies and advanced applications.The recent observation of light-matter quantum condensates in semiconductors has therefore awakened great interest. The bosonic entities in this case are the polaritons - quasi-particles arising from the strong coupling of excitons and photons in a semiconductor microcavity. Due to their very low mass, the condensation occurs at much lower densities and higher temperatures (in the kelvin range) than for atoms. Despite being out-of-equilibrium, they show collective behavior like extended spatial and time coherence, superfluidity, vorticity and parametric oscillation.This proposal aims at the study of polariton condensates in (Al,Ga)As-based microcavities under a tunable periodic potential. This potential will be generated by surface acoustic waves (SAWs), which are particularly well suited to manipulate polariton condensates since their wavelength is smaller than the coherence length of the condensate. They are also capable of coherently modulating both the exciton and the photon creating perfect periodic potentials. And, importantly, and unlike other approaches, the SAW potential is tunable. We have set an important milestone by achieving the growth of the microcavity samples and demonstrating that the modulation of polariton condensates by SAWs is possible. The purpose of this project is to extend these investigations. Our goals include:1. increase the efficiency of modulation of polaritons by SAWs, 2. realize basic studies of polaritons in a SAW lattice 3. perform advanced experiments aimed at the control of the condensate coherence properties and interactions, 4. exploit the former points for the generation of non-classical light states and study of non-equilibrium quantum phase-transitions.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Edgar Cerda, until 9/2015