Hannover 2016 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 71: Quantum Effects: QED IV

Q 71.7: Talk

Friday, March 4, 2016, 16:15–16:30, f442

Lateral Casimir–Polder forces — •Ricardo Oude Weernink and Stefan Yoshi Buhmann — Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

Lateral Casimir–Polder forces can occur when excited-state atoms undergo asymmetric downward circular dipole transitions [1]. Lateral in this regard means parallel to the surface of a metal or dielectric body. As recently observed for the case of a nanofiber, the atoms’ decay leads to asymmetrically emitted fields [2], causing this force.

We study this effect for a simple model geometry: an excited two-state atom is positioned in a vacuum half space close to a half space filled with homogeneous dielectric. By use of macroscopic quantum electrodynamics, the lateral force can be described as a fuction of the system’s Green’s tensor and the atomic dipole moment. Also, a non-vanishing asymmetry term for photons being emitted into the two lateral half spaces can be established. This asymmetry explains the physical origin of the force by virtue of conservation of momentum. Both the force as well as the emission asymmetry show an oscillating behaviour in space, with the oscillations being related to the wave-length of the emitted photons.

[1] Directional spontaneous emission and lateral Casimir-Polder force on an atom close to a nanofiber, S. Scheel, S. Y. Buhmann, C. Clausen and P. Schneeweiss, Phys. Rev. A 92, 043819 (2015).

[2] Quantum state-controlled directional spontaneous emission of photons into a nanophotonic waveguide, R. Mitsch et al., Nature Comm. 5, 5713 (2014).