12,675 research outputs found
Correlated versus Uncorrelated Stripe Pinning: the Roles of Nd and Zn Co-Doping
We investigate the stripe pinning produced by Nd and Zn co-dopants in
cuprates via a renormalization group approach. The two dopants play
fundamentally different roles in the pinning process. While Nd induces a
correlated pinning potential that traps the stripes in a flat phase and
suppresses fluctuations, Zn pins the stripes in a disordered manner and
promotes line meandering. We obtain the zero temperature phase diagram and
compare our results with neutron scattering data. A good agreement is found
between theory and experiment.Comment: To appear at the proceedings of the LLD2K Conference Tsukuba, July
2000, Japan. 4 pages, 2 figure
Electron-Electron Interactions in the Vacuum Polarization of Graphene
We discuss the effect of electron-electron interactions on the static
polarization properties of graphene beyond RPA. Divergent self-energy
corrections are naturally absorbed into the renormalized coupling constant
. We find that the lowest order vertex correction, which is the first
non-trivial correlation contribution, is finite, and about 30% of the RPA
result at strong coupling . The vertex correction leads to
further reduction of the effective charge. Finite contributions to dielectric
screening are expected in all orders of perturbation theory.Comment: 5 pages, 2 figures; published versio
Wave polarizations for a beam-like gravitational wave in quadratic curvature gravity
We compute analytically the tidal field and polarizations of an exact
gravitational wave generated by a cylindrical beam of null matter of finite
width and length in quadratic curvature gravity. We propose that this wave can
represent the gravitational wave that keep up with the high energy photons
produced in a gamma ray burst (GRB) source.Comment: 5 pages, 3 figures, minor corrections, to appear in CQ
Tailoring Graphene with Metals on Top
We study the effects of metallic doping on the electronic properties of
graphene using density functional theory in the local density approximation in
the presence of a local charging energy (LDA+U). The electronic properties are
sensitive to whether graphene is doped with alkali or transition metals. We
estimate the the charge transfer from a single layer of Potassium on top of
graphene in terms of the local charging energy of the graphene sheet. The
coating of graphene with a non-magnetic layer of Palladium, on the other hand,
can lead to a magnetic instability in coated graphene due to the hybridization
between the transition-metal and the carbon orbitals.Comment: 5 pages, 4 figure
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