Light-mediated Magnetism in Cold Atoms
A successful collaboration between the University of Strathclyde (Ivor Kresic, Gordon Robb, Gian-Luca Oppo, Pedro Gomes, Paul Griffin, and Thorsten Ackemann) and the Universite’ Cote d’Azur in Nice, France (Guillaume Labeyrie and Robin Kaiser) under the auspices of the European Network ColOpt, has resulted in a Communications Physics (Vol. 1, 33 (2018)) and an Optica paper (Vol. 5, 1322 (2018)).
By shining laser light on a cloud of cold atoms and reflecting it back with a mirror, domains of spin-polarized atoms spontaneously form and arrange themselves in regular structures. These domains display configurations and phase transitions typical of magnetic systems although the interaction between the atomic spins is not magnetic but mediated by the laser light. Phase diagrams of different magnetic states, including anti-ferromagnetic and ferrimagnetic structures, have been obtained experimentally (see figure) and nicely confirmed in theoretical and numerical models.
Phase diagrams of light-mediated magnetism in cold atoms when changing the magnetic field B = (Bx, By, Bz). AFM: Anti Ferro Magnetic phase. FM: Ferri Magnetic phase.