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arXiv · 1108.2901

Observation of non-conventional spin waves in composite fermion ferromagnets

U. Wurstbauer·S. S. Mandal·D. Majumder·I. Dujovne·T. D. Rhone·B. S. Dennis·A. F. Rigosi·J. K. Jain·A. Pinczuk·K. W. West·L. N. Pfeiffer
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Abstract

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 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.

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U. Wurstbauer, S. S. Mandal, D. Majumder, I. Dujovne, T. D. Rhone, B. S. Dennis, A. F. Rigosi, J. K. Jain, A. Pinczuk, K. W. West, L. N. Pfeiffer. 2011-08-14. Observation of non-conventional spin waves in composite fermion ferromagnets. https://doi.org/10.1103/physrevlett.107.066804

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