Geometrically locked vortex lattices in semiconductor quantum fluids

• Published in: Nature communications Vol. 3; no. 1; p. 1243
• Main Authors: Tosi, G., Christmann, G., Berloff, N.G., Tsotsis, P., Gao, T., Hatzopoulos, Z., Savvidis, P.G., Baumberg, J.J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.12.2012; Nature Publishing Group
• Subjects: 639/301/119/1000; 639/766/119/999; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2255

Macroscopic quantum states can be easily created and manipulated within semiconductor microcavity chips using exciton-photon quasiparticles called polaritons. Besides being a new platform for technology, polaritons have proven to be ideal systems to study out-of-equilibrium condensates. Here we harness the photonic component of such a semiconductor quantum fluid to measure its coherent wavefunction on macroscopic scales. Polaritons originating from separated and independent incoherently pumped spots are shown to phase-lock only in high-quality microcavities, producing up to 100 vortices and antivortices that extend over tens of microns across the sample and remain locked for many minutes. The resultant regular vortex lattices are highly sensitive to the optically imposed geometry, with modulational instabilities present only in square and not triangular lattices. Such systems describe the optical equivalents to one- and two-dimensional spin systems with (anti)-ferromagnetic interactions controlled by their symmetry, which can be reconfigured on the fly, paving the way to widespread applications in the control of quantum fluidic circuits. Polariton condensates provide an arena in which to study interesting non-equilibrium condensate dynamics. Tosi et al . generate stable vortex lattices in a polariton condensate and study their macroscopic wavefunction, uncovering a nonlinear regime for topological defects at high densities.