Dispersion forces such as Casimir forces between bodies, Casimir-Polder forces between atoms and bodies and van der Waals forces between atoms are effective electromagnetic forces that arise as consequences of correlated ground-state fluctuations. We are investigating dispersion forces in and out of thermal equilibrium [1,2,3] that are particularly relevant for long-wavelength atomic transitions as found in Rydberg atoms [4,5], and study universal scaling laws [6] and friction forces [7,8]. 

Dispersion forces occur in a variety of different contexts such as molecular interferometry where they influence the interference pattern of large molecules [9,10], and in diffraction processes of atom clouds off periodic surface potential landscapes [11]. Near nanofibers, we have shown that the Casimir-Polder force on an atom can be laterally tuned by choosing the appropriate atomic state for preparation [12], and the confinement of atoms inside a hollow-core fiber can be used to tune the van der Waals interaction between them [13].

[1] S.Y. Buhmann and S. Scheel, Thermal Casimir versus Casimir-Polder Forces: Equilibrium and Nonequilibrium Forces, Phys. Rev. Lett. 100, 253201 (2008)

[2] S.A. Ellingsen, S.Y. Buhmann, and S. Scheel, Dynamics of thermal Casimir-Polder forces on polar molecules, Phys. Rev. A 79, 052903 (2009)

[3] S.A. Ellingsen, S.Y. Buhmann, and S. Scheel, Temperature-Independent Casimir-Polder Forces Despite Large Thermal Photon Numbers,  Phys. Rev. Lett. 104, 223003 (2010)

[4] J.A. Crosse et al., Thermal Casimir-Polder shifts in Rydberg atoms near metallic surfaces, Phys. Rev. A 82, 010901(R) (2010)

[5] S. Ribeiro, S.Y. Buhmann, T. Stielow, and S. Scheel, Casimir-Polder interaction from exact diagonalization and surface-induced state mixing, EPL 110, 51003 (2015)

[6] S.Y. Buhmann, S. Scheel, and J.R. Babington, Universal Scaling Laws for Dispersion Interactions, Phys. Rev. Lett. 104, 070404 (2010)

[7] S. Scheel and S.Y. Buhmann, Casimir-Polder forces on moving atoms, Phys. Rev. A 80, 042902 (2009)

[8] F. Intravaia et al., Friction forces on atoms after acceleration, J. Phys.: Condensed Matter 27, 214020 (2015)

[9] C. Brand et al., A Green’s function approach to modeling molecular diffraction
in the limit of ultra-thin gratings, Ann. d. Phys. 527, 580 (2015)

[10] J. Fiedler and S. Scheel, Casimir-Polder potentials on extended molecules, Ann. d. Phys. 527, 570 (2015)

[11] H. Bender et al., Probing Atom-Surface Interactions by Diffraction of Bose-Einstein Condensates, Phys. Rev. X 4, 011029 (2014)

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

[13] H.R. Haakh and S. Scheel, Modified and controllable dispersion interaction in a one-dimensional waveguide geometry, Phys. Rev. A 91, 052707 (2015)