Ryan Behunin

Quantum friction and fluctuation theorems

We use general concepts of statistical mechanics to compute the quantum frictional force on an atom moving at constant velocity above a planar surface. We derive the zero-temperature frictional force using a non-equilibrium fluctuation-dissipation relation, and show that in the large-time, steady-state regime quantum friction scales as the cubic power of the atoms velocity. We also discuss how approaches based on Wigner-Weisskopf and quantum regression approximations fail to predict the correct steady-state zero temperature frictional force, mainly due to the low frequency nature of quantum friction.

Modeling electrostatic patch effects in Casimir force measurements

Electrostatic patch potentials give rise to forces between neutral conductors at distances in the micrometer range and must be accounted for in the analysis of Casimir force experiments. In this paper we develop a quasilocal model for describing random potentials on metallic surfaces. In contrast to some previously published results, we find that patches may provide a significant contribution to the measured signal and thus may be a more important systematic effect than was previously anticipated. Additionally, patches may render the experimental data at distances below 1 μm compatible with theoretical predictions based on the Drude model.

Kelvin probe force microscopy of metallic surfaces used in Casimir force measurements

Kelvin probe force microscopy at normal pressure was performed by two different groups on the same Au-coated planar sample used to measure the Casimir interaction in a sphere-plane geometry. The obtained voltage distribution was used to calculate the separation dependence of the electrostatic pressure

Electrostatic patch effects in Casimir-force experiments performed in the sphere-plane geometry

{P}_{\mathrm{res}}(D)

Nonequilibrium forces between atoms and dielectrics mediated by a quantum field

in the configuration of the Casimir experiments. In the calculation it was assumed that the potential distribution in the sphere has the same statistical properties as the measured one, and that there are no correlation effects on the potential distributions due to the presence of the other surface. The result of this calculation, using the currently available knowledge, is that

Forward Brillouin scattering in hollow-core photonic bandgap fibers

{P}_{\mathrm{res}}(D)

Limits on the accuracy of force sensing at short separations due to patch potentials

does not explain the magnitude or the separation dependence of the difference

Guided-wave Brillouin scattering in air

\ensuremath{\Delta}P(D)

Theory of optomechanics: Oscillator-field model of moving mirrors

between the measured Casimir pressure and the one calculated using a Drude model for the electromagnetic response of Au. We discuss in the conclusions the points which have to be checked out by future work, including the influence of pressure and a more accurate determination of the patch distribution, in order to confirm these results.

Failure of local thermal equilibrium in quantum friction

Patch potentials arising from the polycrystalline structure of material samples may contribute significantly to measured signals in Casimir force experiments. Most of these experiments are performed in the sphere-plane geometry; yet, up to now all analysis of patch effects has been taken into account using the proximity force approximation which, in essence, treats the sphere as a plane. In this paper we present the exact solution for the electrostatic patch interaction energy in the sphere-plane geometry and derive exact analytical formulas for the electrostatic patch force and minimizing potential. We perform numerical simulations to analyze the distance dependence of the minimizing potential as a function of patch size, and we quantify the sphere-plane patch force for a particular patch layout. Once the patch potentials on both surfaces are measured by dedicated experiments our formulas can be used to exactly quantify the sphere-plane patch force in the particular experimental situation.