17,543 research outputs found
Phase Diagram of the Holstein-Hubbard Two-Leg Ladder
Using a functional renormalization group method, we obtain the phase diagram
of the two-leg ladder system within the Holstein-Hubbard model, which includes
both electron-electron and electron-phonon interactions. Our renormalization
group technique allows us to analyze the problem for both weak and strong
electron-phonon coupling. We show that, in contrast results from conventional
weak coupling studies, electron-phonon interactions can dominate
electron-electron interactions because of retardation effects.Comment: 4 page
Optical Spectroscopic Survey of High-latitude WISE-selected Sources
We report on the results of an optical spectroscopic survey at high Galactic latitude (|b| ≥ 30°) of a sample of WISE-selected targets, grouped by WISE W1 (λ_eff = 3.4 μm) flux, which we use to characterize the sources WISE detected. We observed 762 targets in 10 disjoint fields centered on ultraluminous infrared galaxy candidates using DEIMOS on Keck II. We find 0.30 ± 0.02 galaxies arcmin–2 with a median redshift of z = 0.33 ± 0.01 for the sample with W1 ≥ 120 μJy. The foreground stellar densities in our survey range from 0.23 ± 0.07 arcmin–2 to 1.1 ± 0.1 arcmin–2 for the same sample. We obtained spectra that produced science grade redshifts for ≥90% of our targets for sources with W1 flux ≥120 μJy that also had an i-band flux gsim 18 μJy. We used this for targeting very preliminary data reductions available to the team in 2010 August. Our results therefore present a conservative estimate of what is possible to achieve using WISE's Preliminary Data Release for the study of field galaxies
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Reversible writing of high-mobility and high-carrier-density doping patterns in two-dimensional van der Waals heterostructures
A key feature of two-dimensional materials is that the sign and concentration of their carriers can be externally controlled with techniques such as electrostatic gating. However, conventional electrostatic gating has limitations, including a maximum carrier density set by the dielectric breakdown, and ionic liquid gating and direct chemical doping also suffer from drawbacks. Here, we show that an electron-beam-induced doping technique can be used to reversibly write high-resolution doping patterns in hexagonal boron nitride-encapsulated graphene and molybdenum disulfide (MoS2) van der Waals heterostructures. The doped MoS2 device exhibits an order of magnitude decrease of subthreshold swing compared with the device before doping, whereas the doped graphene devices demonstrate a previously inaccessible regime of high carrier concentration and high mobility, even at room temperature. We also show that the approach can be used to write high-quality p–n junctions and nanoscale doping patterns, illustrating that the technique can create nanoscale circuitry in van der Waals heterostructures
Anomalous magnetic moment in parity-conserving QED3
In this article we derive the anomalous magnetic moment of fermions in
(2+1)-dimensional parity-conserving QED3, in the presence of an externally
applied constant magnetic field. We use a spectral representation of the photon
propagator to avoid infrared divergences. We also discuss the scaling with the
magnetic field intensity in the case of strong external fields, where there is
dynamical mass generation for fermions induced by the magnetic field itself
(magnetic catalysis). The results of this paper may be of relevance to the
physics of high-temperature superconductors.Comment: 27 pages LATEX, three eps figures incorporate
Radiative Corrections to Electron-Proton Scattering
The radiative corrections to elastic electron-proton scattering are analyzed
in a hadronic model including the finite size of the nucleon. For initial
electron energies above 8 GeV and large scattering angles, the proton vertex
correction in this model increases by at least two percent the overall factor
by which the one-photon exchange (Rosenbluth) cross section must be multiplied.
The contribution of soft photon emission is calculated exactly. Comparison is
made with the generally used expressions previously obtained by Mo and Tsai.
Results are presented for some kinematics at high momentum transfer.Comment: 31 pages, 4 figure
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