Lijun Zhu, Vivek Aji, Chandra M. Varma
The zero gap non-interacting electronic structure of bilayer graphene is
unstable to infinitesimal interactions. Indeed a gap is found in experiments
but none of the states proposed so far is consistent with its properties. Here
we show that a Magneto-Electric(ME) state is consistent with the experimental
observations. This state breaks time-reversal symmetry through a pair of
spontaneously generated current loops in each layer, and has odd-parity with
respect to the two layers. We also show that such a state wins over the
Haldane-type state with spontaneous quantum Hall effect (AHE) which has even
parity, for large enough interactions and low enough temperature. We also
propose further experiments to confirm this conclusion and the possibility that
at higher temperatures the Haldane-type state is realized.
View original:
http://arxiv.org/abs/1202.0821
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