Collective modes and skyrmion excitations in graphene SU"4… quantum Hall ferromagnets

By Kun Yang, Allan H. MacDonald. 2006

134 citations recorded by the source corpus.

Graphene exhibits quantum Hall ferromagnetism in which an approximate $SU(4)$ symmetry involving spin and valley degrees of freedom is spontaneously broken. We construct a set of integer and fractional quantum Hall states that break the $SU(4)$ spin (valley) symmetry, and study their neutral and charged excitations. Several properties of these ferromagnets can be evaluated analytically in the $SU(4)$ symmetric limit, including the full collective-mode spectrum at integer fillings. By constructing explicit wave functions we show that the lowest-energy skyrmion states carry charge $\ifmmode\pm\else\textpm\fi{}1$ for any integer filling, and that skyrmions are the lowest-energy-charged excitations for graphene Landau-level index $\ensuremath{\mid}n\ensuremath{\mid}\ensuremath{\leqslant}3$. We also show that the skyrmion lattice states which occur near integer-filling factors support four gapless collective-mode branches in the presence of full $SU(4)$ symmetry. Comparisons are made with the more familiar $SU(2)$ quantum Hall ferromagnets studied previously.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/34b0224fddedc566b61c3c1941512228da0aea11

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In Atomic and Molecular Physics, and Optics

1. E. Rossi
2. E. Hwang
3. S. Adam
4. M. Goerbig
5. N. M. R. Peres
6. Farhan Rana
7. Francisco Guinea
8. K. Novoselov

In Materials Chemistry

1. E. Rossi
2. E. Hwang
3. S. Adam
4. M. Goerbig
5. N. M. R. Peres
6. Francisco Guinea
7. Farhan Rana
8. K. Novoselov

Citations in the corpus

• Electronic properties of graphene in a strong magnetic field (2010, background): “V.B.1 yields the number of residual symmetry transformations (Yang et al., 2006) 2k(N − k)+ 2(N − 1), where the first term describes the Goldstone modes of the ferromagnetic ground state, and the second one corresponds to the N − 1 internal modes of the skyrmion excitation.”
• Electronic transport in two-dimensional graphene (2010, background): “…of the theories the spin/valley degeneracy is lifted due to interaction effects (Abanin et al., 2007b; Alicea and Fisher, 2006; Ezawa, 2007, 2008; Goerbig et al., 2006; Gusynin et al., 2006; Herbut, 2007; Nomura and MacDonald, 2006; Yang et al., 2006), in particular, electron-electron interactions.”