270 research outputs found
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
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