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Pumping of Bose-Einstein-Condensed Magnons Yaroslav Tserkovnyak , University of California-Los Angeles, DMR 0840965.
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Pumping of Bose-Einstein-Condensed MagnonsYaroslavTserkovnyak, University of California-Los Angeles, DMR 0840965 Bose-Einstein condensation of a dilute bosonic gas, one of the most basic and fascinating macroscopic quantum phenomena, has eluded solid-state realization, barring transient phenomena in pump-probe experiments on trapped photons, excitons, or magnons. We theoretically propose a new route towards realization of a steady-state quasiequilibrium condensate of magnons, fomented and controlled by a simultaneous application of a temperature bias normal to a conventional magnetic heterostructure and electric current tangentially to it. If realized, this opens a possibility of inducing magnonsuperfluidity in spintronic devices based on magnetic insulators, which may in principle be achieved even at room temperature. Dynamic phase diagram, as a function of temperature bias (vertical axis) and tangential current bias (horizontal axis) applied to platinum/magnetic insulator bilayer. Bender, Duine, and Tserkovnyak, Phys. Rev. Lett.108, 246601 (2012)
+ + + + + + - - - - - - Physics of Magnetic FluidsYaroslavTserkovnyak, University of California-Los Angeles, DMR 0840965 Magnetic fluids, such as ferrofluids and magnetorheological fluids, provide some of the most important and useful examples of smart fluids, whose physical properties can be dramatically controlled by magnetic fields. This year, UCLA organized a miniworkshop on magnetic fluids, as part of its High School Nanoscience Program, for the area’s high school teachers. We have demonstrated experiments on ferrofluids and provided the teachers with lab supplies to take these demos to their schools. I made faculty presentation on ferrofluids, as an example of pattern formation and emergent behavior in physics, starting with simple but interacting ingredients. Minimization of dipolar energy by vertical elongation of a fluid, against gravitational and capillary forces. Spontaneous formation of a ferrofluid pattern, as a result, at a critical magnetic field.