Abstract
At half-filling of the fourfold degenerate Landau levels in graphene, the ground states are spin-polarized quantum Hall states that support spin skyrmion excitations for . Working in the Hartree-Fock approximation, we compute the excitation energy of an unbound spin skyrmion-antiskyrmion excitation as a function of the Zeeman coupling strength for these Landau levels. We find for both the bare and screened Coulomb interactions that the spin skyrmion-antiskyrmion excitation energy is lower than the excitation energy of an unbound spin- electron-hole pair in a finite range of Zeeman coupling in Landau levels . This range decreases rapidly for increasing Landau level index and is extremely small for For valley skyrmions, which should be present at and fillings of the Landau levels , we show that screening corrections are more important in the latter case. It follows that an unbound valley skyrmion-antiskyrmion excitation has lower energy at filling than at We compare our results with recent experiments on spin and valley skyrmion excitations in graphene.
4 More- Received 27 July 2013
DOI:https://doi.org/10.1103/PhysRevB.88.115417
©2013 American Physical Society