Observation of non-conventional spin waves in composite fermion ferromagnets

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.

4 pages, 4 figures

References in corpus (2)

• Splitting of Long-Wavelength Modes of the Fractional Quantum Hall Liquid at $\nu =1/3$
• Higher Energy Composite Fermion Levels in the Fractional Quantum Hall Effect

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