Electromagnetic response and effective gauge theory of graphene in a magnetic field

The electromagnetic response of graphene in a magnetic field is studied, with particular emphasis on the quantum features of its ground state (vacuum). The graphene vacuum, unlike in conventional quantum Hall systems, is a dielectric medium and carries an appreciable amount of electric and magnetic susceptibilities. The dielectric effect grows rapidly with increasing filling factor nu in such a way that reflects the 'relativistic' Landau-level characteristics of graphene as well as its valley and spin degeneracy. A close look into the dielectric function also reveals that the Coulomb interaction is efficiently screened on the scale of the magnetic length, leading to a prominent reduction of the exciton spectra in graphene. In addition, an effective gauge theory of graphene is constructed out of the response. It is pointed out thereby that the electric susceptibility is generally expressed as a ratio of the Hall conductance to the Landau gap.Comment: 9 pages, 3 figures, revtex, corrected typo

Renormalization and cyclotron resonance in bilayer graphene with weak electron-hole asymmetry

Cyclotron resonance in bilayer graphene is studied with weak electron-hole asymmetry, suggested by experiment, taken into account and with the focus on many-body corrections that evade Kohn's theorem. It is shown by direct calculation that the theory remains renormalizable to O(e^2) in the presence of electron-hole asymmetry parameters, and a general program to carry out renormalization for graphene under a magnetic field is presented. Inclusion of electron-hole asymmetry in part improves the theoretical fit to the existing data and the data appear to indicate the running of the renormalized velocity factor with the magnetic field, which is a key consequence of renormalization.Comment: 10 pages, 5 figures, revtex, published versio

Superfield formulation of central charge anomalies in two-dimensional supersymmetric theories with solitons

A superfield formulation is presented of the central charge anomaly in quantum corrections to solitons in two-dimensional theories with N=1 supersymmetry. Extensive use is made of the superfield supercurrent, that places the supercurrent J^{mu}_{alpha}, energy-momentum tensor Theta^{mu nu} and topological current zeta^{mu} in a supermultiplet, to study the structure of supersymmetry and related superconformal symmetry in the presence of solitons. It is shown that the supermultiplet structure of (J^{mu}_{alpha}, Theta^{mu nu}, zeta^{mu}) is kept exact while the topological current zeta^{\mu} acquires a quantum modification through the superconformal anomaly. In addition, the one-loop superfield effective action is explicitly constructed to verify the BPS saturation of the soliton spectrum as well as the effect of the anomaly.Comment: 9 pages, Revtex, one reference adde

Current distributions and the de Haas-van Alphen oscillation in a planar system of Hall electrons

The current distribution is studied for a finite-width two-dimensional system of Hall electrons, with a clear distinction drawn between the equilibrium edge current and the Hall current. It is pointed out that both the distribution and direction of the equilibrium edge current change dramatically as the number of electron edge states increases, and that this alternating edge current is another manifestation of the de Haas-van Alphen effect. The Hall-current distribution is substantially different from the edge current distribution, and it is shown numerically that the fast-traveling electrons along the sample edge are not the main carriers of the Hall current.Comment: 20 pages, Revtex, 6 figures, final version as publishe