- 著者
- Hamamoto Yuji Kawarabayashi Tohru Aoki Hideo Hatsugai Yasuhiro
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.88, no.19, pp.195141, 2013-11
- 被引用文献数
- 2 1
Motivated by the recent experiments indicating a spin-unpolarized ν=0 quantum Hall state in graphene, we theoretically investigate the ground state based on the many-body problem projected onto the n=0 Landau level. For an effective model with the on-site Coulomb repulsion and antiferromagnetic exchange couplings, we show that the ground state is a doubly degenerate spin-resolved chiral condensate in which all the zero-energy states with up spin are condensed into one chirality, while those with down spin to the other. This can be exactly shown for an Ising-type exchange interaction. The charge gap due to the on-site repulsion in the ground state is shown to grow linearly with the magnetic field, in qualitative agreement with the experiments.
1 0 0 0 OA Chiral condensate with topological degeneracy in graphene and its manifestation in edge states
- 著者
- Hamamoto Yuji Aoki Hideo Hatsugai Yasuhiro
- 出版者
- American Physical Society
- 雑誌
- Physical review B (ISSN:10980121)
- 巻号頁・発行日
- vol.86, no.20, pp.205424, 2012-11
- 被引用文献数
- 11
The role of chiral symmetry in many-body states of graphene in strong magnetic fields is theoretically studied with the honeycomb lattice model. For a spin-split Landau level where the leading electron-electron interaction is the nearest-neighbor repulsion, a chiral condensate is shown to be, within the subspace of the n=0 Landau level, an exact many-body ground state having a finite gap, for which a calculation of the Chern number reveals that the ground state is a Hall insulator with a topological degeneracy of two. The topological nature of the ground state is shown to manifest itself as a Kekuléan bond order along armchair edges, while the pattern melts in the bulk due to quantum fluctuations. These can be regarded as a realization of the bulk-edge correspondence that is peculiar to a chiral-symmetric system. We have also obtained the ground state when point defects are introduced in the honeycomb lattice to reveal how the presence or absence of the chiral symmetry affects the defect states.