F. Bruckmann, P. V. Buividovich, T. Sulejmanpasic
We describe a generic mechanism by which a system of Dirac fermions which carry an additional quantum number (isospin) acquires electric charge when the system is subject to an isospin chemical potential and a superposition of a normal magnetic field and a magnetic field which distinguishes the isospin. A nontrivial feature of fermions in the background of such gauge fields is that the electric charge appears due to nonzero isospin chemical potential and vice versa. The charge is accumulated since the degeneracies of occupied lowest Landau levels for particles of positive isospin and anti-particles of negative isospin are different. We discuss two physical systems where this phenomenon can be realized. One is monolayer graphene where the isospin is associated with two valleys in the Brillouin zone and the strain-induced pseudo-magnetic field acts differently on charge carriers in different valleys. Another is hot QCD, for which the role of isospin is played by the color of quarks. In the latter case the described mechanism should manifest itself in a decrease of charge fluctuations in the presence of an external magnetic field.
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http://arxiv.org/abs/1303.1710
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