16 research outputs found
Scalar Casimir-Polder forces for uniaxial corrugations
We investigate the Dirichlet-scalar equivalent of Casimir-Polder forces
between an atom and a surface with arbitrary uniaxial corrugations. The
complexity of the problem can be reduced to a one-dimensional Green's function
equation along the corrugation which can be solved numerically. Our technique
is fully nonperturbative in the height profile of the corrugation. We present
explicit results for experimentally relevant sinusoidal and sawtooth
corrugations. Parameterizing the deviations from the planar limit in terms of
an anomalous dimension which measures the power-law deviation from the planar
case, we observe up to order-one anomalous dimensions at small and intermediate
scales and a universal regime at larger distances. This large-distance
universality can be understood from the fact that the relevant fluctuations
average over corrugation structures smaller than the atom-wall distance.Comment: 25 pages, 7 figure
Quantum reflection from an oscillating surface
We describe an experimentally realistic situation of the quantum reflection
of helium atoms from an oscillating surface. The temporal modulation of the
potential induces clear sidebands in the reflection probability as a function
of momentum. Theses sidebands could be exploited to slow down atoms and
molecules in the experiment.Comment: 9 pages, 4 figure
Nonperturbative access to Casimir-Polder forces
We discuss the scalar analogue of the Casimir-Polder force between a sphere
and a uniaxially corrugated surface with Dirichlet boundary conditions.
Presenting a formulation that is nonperturbative in the height profile of the
surface, we give explicit numerical results for a sinuosoidal corrugation
profile.Comment: 5 pages, 1 figure. Talk given by B.D. at the Ninth Conference on
Quantum Field Theory under the Influence of External Conditions (QFEXT 09),
21-25 September 2009, Oklahoma, US
Longitudinal Atomic Beam Spin Echo Experiments: A possible way to study Parity Violation in Hydrogen
We discuss the propagation of hydrogen atoms in static electric and magnetic
fields in a longitudinal atomic beam spin echo (lABSE) apparatus. Depending on
the choice of the external fields the atoms may acquire both dynamical and
geometrical quantum mechanical phases. As an example of the former, we show
first in-beam spin rotation measurements on atomic hydrogen, which are in
excellent agreement with theory. Additional calculations of the behaviour of
the metastable 2S states of hydrogen reveal that the geometrical phases may
exhibit the signature of parity-(P-)violation. This invites for possible future
lABSE experiments, focusing on P-violating geometrical phases in the lightest
of all atoms.Comment: 6 pages, 4 figure
Einstein-Hopf Drag, Doppler Shift of Thermal Radiation and Blackbody Drag: Three Perspectives on Quantum Friction
The thermal friction force acting on an atom moving relative to a thermal photon bath has recently been calculated on the basis of the fluctuation-dissipation theorem. The thermal fluctuations of the electromagnetic field give rise to a drag force on an atom provided one allows for dissipation of the field energy via spontaneous emission. The drag force exists if the atomic polarizability has a nonvanishing imaginary part. Here, we explore alternative derivations. The damping of the motion of a simple harmonic oscillator is described by radiative reaction theory (result of Einstein and Hopf), taking into account the known stochastic fluctuations of the electromagnetic field. Describing the excitations of the atom as an ensemble of damped harmonic oscillators, we identify the previously found expressions as generalizations of the Einstein-Hopf result. In addition, we present a simple explanation for blackbody friction in terms of a Doppler shift of the thermal radiation in the inertial frame of the moving atom: The atom absorbs blue-shifted photons from the front and radiates off energy in all directions, thereby losing energy. The original plus the two alternative derivations provide for additional confirmation of an intriguing quantum friction effect, and leave no doubt regarding its existence
Noble Gas, Alkali and Alkaline Atoms Interacting with a Gold Surface
The attractive branch of the interaction potentials with the surface of gold have been computed for a large variety of atomic systems: the hydrogen atom, noble gases (He, Ne, Ar, Kr, Xe), alkali atoms (Li, Na, K, Rb, Cs) and alkaline atoms (Be, Mg, Ca, Sr, Ba). The results include highly accurate dynamic polarizabilities for the helium atom calculated using a variational method and explicitly correlated wavefunctions. For other atoms considered we used the data available in the literature. The interaction potentials include both the effects of retardation of the electromagnetic interactions and a realistic representation of the optical response function of gold (beyond the approximation of a perfect conductor). An explicit comparison of our result to the interaction between an atom and a perfect conductor is given. © 2010 World Scientific Publishing Company