65,059 research outputs found
Implementation of a single femtosecond optical frequency comb for rovibrational cooling
We show that a single femtosecond optical frequency comb may be used to
induce two-photon transitions between molecular vibrational levels to form
ultracold molecules, e.g., KRb. The phase across an individual pulse in the
pulse train is sinusoidally modulated with a carefully chosen modulation
amplitude and frequency. Piecewise adiabatic population transfer is fulfilled
to the final state by each pulse in the applied pulse train providing a
controlled population accumulation in the final state. Detuning the pulse train
carrier and modulation frequency from one-photon resonances changes the time
scale of molecular dynamics but leads to the same complete population transfer
to the ultracold state. A standard optical frequency comb with no modulation is
shown to induce similar dynamics leading to rovibrational cooling.Comment: 14 pages, 7 figure
Effect of charged impurities on graphene thermoelectric power near the Dirac point
In graphene devices with a varying degree of disorders as characterized by
their carrier mobility and minimum conductivity, we have studied the
thermoelectric power along with the electrical conductivity over a wide range
of temperatures. We have found that the Mott relation fails in the vicinity of
the Dirac point in high-mobility graphene. By properly taking account of the
high temperature effects, we have obtained good agreement between the Boltzmann
transport theory and our experimental data. In low-mobility graphene where the
charged impurities induce relatively high residual carrier density, the Mott
relation holds at all gate voltages
Plasmon geometric phase and plasmon Hall shift
The collective plasmonic modes of a metal comprise a pattern of charge
density and tightly-bound electric fields that oscillate in lock-step to yield
enhanced light-matter interaction. Here we show that metals with non-zero Hall
conductivity host plasmons with a fine internal structure: they are
characterized by a current density configuration that sharply departs from that
of ordinary zero Hall conductivity metals. This non-trivial internal structure
dramatically enriches the dynamics of plasmon propagation, enabling plasmon
wavepackets to acquire geometric phases as they scatter. Strikingly, at
boundaries these phases accumulate allowing plasmon waves that reflect off to
experience a non-reciprocal parallel shift along the boundary displacing the
incident and reflected plasmon trajectories. This plasmon Hall shift, tunable
by Hall conductivity as well as plasmon wavelength, displays the chirality of
the plasmon's current distribution and can be probed by near-field photonics
techniques. Anomalous plasmon dynamics provide a real-space window into the
inner structure of plasmon bands, as well as new means for directing plasmonic
beams
The Possible State X(1600)
The interesting state X(1600) with can't be a
conventional meson in the quark model. Using a mixed interpolating
current with different color configurations, we investigate the possible
existence of X(1600) in the framework of QCD finite energy sum rules. Our
results indicate that both the "hidden color" and coupled channel effects may
be quite important in the multiquark system. We propose several reactions to
look for this state.Comment: axodraw.sty include
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