1,846 research outputs found
Synthetic 3D Spin-Orbit Coupling
We describe a method for creating a three-dimensional analogue to Rashba
spin-orbit coupling in systems of ultracold atoms. This laser induced coupling
uses Raman transitions to link four internal atomic states with a tetrahedral
geometry, and gives rise to a Dirac point that is robust against environmental
perturbations. We present an exact result showing that such a spin-orbit
coupling in a fermionic system always rise to a molecular bound state.Comment: 4 pages, 6 figure
A Bose-Einstein Condensate in a Uniform Light-induced Vector Potential
We use a two-photon dressing field to create an effective vector gauge
potential for Bose-condensed Rb atoms in the F=1 hyperfine ground state. The
dressed states in this Raman field are spin and momentum superpositions, and we
adiabatically load the atoms into the lowest energy dressed state. The
effective Hamiltonian of these neutral atoms is like that of charged particles
in a uniform magnetic vector potential, whose magnitude is set by the strength
and detuning of Raman coupling. The spin and momentum decomposition of the
dressed states reveals the strength of the effective vector potential, and our
measurements agree quantitatively with a simple single-particle model. While
the uniform effective vector potential described here corresponds to zero
magnetic field, our technique can be extended to non-uniform vector potentials,
giving non-zero effective magnetic fields.Comment: 5 pages, submitted to Physical Review Letter
Theory of the tunneling resonances of the bilayer electron systems in strong magnetic field
We develop a theory for the anomalous interlayer conductance peaks observed
in bilayer electron systems at nu=1. Our model shows the that the size of the
peak at zero bias decreases rapidly with increasing in-plane magnetic field,
but its location is unchanged. The I-V characteristic is linear at small
voltages, in agreement with experimental observations. In addition we make
quantitative predictions for how the inter-layer conductance peaks vary in
position with in-plane magnetic field at high voltages. Finally, we predict
novel bi-stable behavior at intermediate voltages.Comment: 5 pages, 2 figure
Persistent Currents and Dissipation in Narrow Bilayer Quantum Hall Bars
Bilayer quantum Hall states support a flow of nearly dissipationless
staggered current which can only decay through collective channels. We study
the dominant finite-temperature dissipation mechanism which in narrow bars is
driven by thermal nucleation of pseudospin solitons. We find the
finite-temperature resistivity, predict the resulting staggered current-voltage
characteristics, and calculate the associated zero-temperature critical
staggered current and gate voltage.Comment: 4 pgs. REVTeX, 3 eps figure
Spin Transition in Strongly Correlated Bilayer Two Dimensional Electron Systems
Using a combination of heat pulse and nuclear magnetic resonance techniques
we demonstrate that the phase boundary separating the interlayer phase coherent
quantum Hall effect at in bilayer electron gases from the weakly
coupled compressible phase depends upon the spin polarization of the nuclei in
the host semiconductor crystal. Our results strongly suggest that, contrary to
the usual assumption, the transition is attended by a change in the electronic
spin polarization.Comment: 4 pages, 3 postscript figur
Brownian motion of solitons in a Bose-Einstein Condensate
For the first time, we observed and controlled the Brownian motion of
solitons. We launched solitonic excitations in highly elongated
BECs and showed that a dilute background of impurity atoms in a different
internal state dramatically affects the soliton. With no impurities and in
one-dimension (1-D), these solitons would have an infinite lifetime, a
consequence of integrability. In our experiment, the added impurities scatter
off the much larger soliton, contributing to its Brownian motion and decreasing
its lifetime. We describe the soliton's diffusive behavior using a quasi-1-D
scattering theory of impurity atoms interacting with a soliton, giving
diffusion coefficients consistent with experiment.Comment: 4 figure
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