Wess-Zumino-Witten Terms in Graphene Landau Levels
Fig 1: AF (left) and Kekulé VBS states of bilayer graphene. The blue (red) lines indicate the honeycomb lattice of the top (bottom) layer. The ellipses in the VBS state denote the links between the top and bottom layers which are equivalently distorted with respect to the parent lattice*. [Copyright 2015 by the American Physical Society]
In a recent editor-suggested article* in Physical Review Letters, grad student Junhyun Lee and Prof. Subir Sachdev consider the interplay between the antiferromagnetic and Kekulé valence bond solid orderings in the zero energy Landau levels of neutral monolayer and bilayer graphene. They phusicists establish the presence of Wess-Zumino-Witten terms between these orders, which implies that their quantum fluctuations are described by the deconfined critical theories of quantum spin systems. They then present implications for experiments, including the possible presence of excitonic superfluidity in bilayer graphene.
*Junhyun Lee and Subir Sachdev, "Wess-Zumino-Witten Terms in Graphene Landau Levels," Phys. Rev. Lett. 114, 226801 | DOI: http://dx.doi.org/10.1103/PhysRevLett.114.226801