Observation of Nonconventional Spin Waves in Composite-Fermion Ferromagnets

U. Wurstbauer, D. Majumder, S. S. Mandal, I. Dujovne, T. D. Rhone, B. S. Dennis, A. F. Rigosi, J. K. Jain, A. Pinczuk, K. W. West, L. N. Pfeiffer
2011 Physical Review Letters  
We find unexpected low energy excitations of fully spin-polarized composite-fermion ferromagnets in the fractional quantum Hall liquid, resulting from a complex interplay between a topological order manifesting through new energy levels and a magnetic order due to spin polarization. The lowest energy modes, which involve spin reversal, are remarkable in displaying unconventional negative dispersion at small momenta followed by a deep roton minimum at larger momenta. This behavior results from a
more » ... nontrivial mixing of spin-wave and spin-flip modes creating a spin-flip excitonic state of composite-fermion particle-hole pairs. The striking properties of spin-flip excitons imply highly tunable mode couplings that enable fine control of topological states of itinerant two-dimensional ferromagnets.
doi:10.1103/physrevlett.107.066804 pmid:21902358 fatcat:fadc3muygrcblohy7b3yjbwaou