Half-solitons in a polariton quantum fluid behave like magnetic monopoles

• Published in: Nature physics Vol. 8; no. 10; pp. 724 - 728
• Main Authors: Hivet, R., Flayac, H., Solnyshkov, D. D., Tanese, D., Boulier, T., Andreoli, D., Giacobino, E., Bloch, J., Bramati, A., Malpuech, G., Amo, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.10.2012; Nature Publishing Group; Nature Publishing Group [2005-....]
• Subjects: 639/766/119/1000; 639/766/119/999; 639/766/400/2797; Atomic; Bose-Einstein condensates; Classical and Continuum Physics; Complex Systems; Condensed Matter; Condensed Matter Physics; Crystal defects; Crystals; Electrons; Elementary particles; Excitation; Excitons; Ferromagnetism; Fluid dynamics; Ice; letter; Magnetic fields; Magnetic monopoles; Mathematical and Computational Physics; Molecular; Monopoles; Optical and Plasma Physics; Optics; Particle physics; Physics; Physics and Astronomy; Polaritons; Quantum Physics; Semiconductors; Solitary waves; Solitons; Spin ice; Texture; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2406

An analogue of a magnetic monopole is now observed in a condensed state of light–matter hybrid particles known as cavity polaritons. Spin-phase excitations of the polariton fluid are accelerated along the cavity under the influence of a magnetic field—just as if they were single magnetic charges. Magnetic monopoles 1 are point-like sources of magnetic field, never observed as fundamental particles. This has triggered the search for monopole analogues in the form of emergent particles in the solid state, with recent observations in spin-ice crystals 2 , 3 , 4 and one-dimensional ferromagnetic nanowires 5 . Alternatively, topological excitations of spinor Bose–Einstein condensates have been predicted to demonstrate monopole textures 6 , 7 , 8 . Here we show the formation of monopole analogues in an exciton–polariton spinor condensate hitting a defect potential in a semiconductor microcavity. Oblique dark solitons are nucleated in the wake of the defect 9 , 10 in the presence of an effective magnetic field acting on the polariton pseudo-spin 11 . The field splits the integer soliton into a pair of oblique half-solitons 12 of opposite magnetic charge, subject to opposite effective magnetic forces. These mixed spin-phase excitations thus behave like one-dimensional monopoles 13 . Our results open the way to the generation of stable magnetic currents in photonic quantum fluids.