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In chiral magnets spin-orbit interactions in combination with thermal fluctuations stabilize magnetic whirls, so-called skyrmions. These skyrmions can be manipulated by tiny currents due to a very efficient Berry phase coupling of electronic current and magnetic texture. The effect of these Berry phases can be described by effective "emergent" electromagnetic fields [1]. A change of topology, e.g., during a phase transition, has to occur by singular magnetic configurations [2] which act as sources and sinks of the emergent magnetic flux. Thereby they can be viewed as emergent magnetic monopols.
Time permitting, we also discuss how the spin-orbit entanglement in phase space can lead to an effective charge of the skyrmion which is topologically quantized in insulators.
[1] Emergent electrodynamics of skyrmions in a chiral magnet, T. Schulz, R. Ritz, A. Bauer, M. Halder, M. Wagner, C. Franz, and C. Pfleiderer, K. Everschor, M. Garst, and A. Rosch, Nature Physics, 8, 301 (2012) [2] Unwinding of a skyrmion lattice by magnetic monopoles, P. Milde, D. Köhler, J. Seidel, L. Eng, A. Bauer, A. Chacon, C. Pfleiderer, S. Buhrandt, A. Rosch, Science, accepted (2013). |
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