1105.1989 (Stefan Uebelacker et al.)

Instabilities of quadratic band crossing points    [PDF]

Stefan Uebelacker, Carsten Honerkamp

Using a functional renormalization group approach, we study
interaction-driven instabilities in quadratic band crossing point two-orbital
models in two dimensions, extending a previous study of Sun et al. [1]. The
wavevector-dependence of the Bloch eigenvectors of the free Hamiltonian causes
interesting instabilities toward spin nematic, quantum anomalous Hall and
quantum spin Hall states. In contrast with other known examples of
interaction-driven topological insulators, in the system studied here, the QSH
state occurs at arbitrarily small interaction strength and for rather simple
intra- and inter-orbital repulsions.

View original: http://arxiv.org/abs/1105.1989