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Physics Colloquium


27.11.2017 5:15 p.m., room: T-1004
Dr. Helmut Schultheiss (Helmholtz-Zentrum Dresden-Rossendorf)
Magnon Transport in Spin Textures
11.12.2017 5:15 p.m., room: T-1004
Professor Rolf Haug (Universität Hannover)
Shot Noise in Single-Electron Tunneling through Quantum Dots: A Toolbox to Study Quantum Physics
8.1.2018 5:15 p.m., room: T-1004
Ursula Wurstbauer (Walter Schottky Institut, TU München)
Exzitonen, Phononen und Elektronen in van der Waals Heterostrukturen
22.1.2018 5:15 p.m., room: T-1004
Prof. Dr. Paulo A. Maia Neto (Universidade Federal do Rio de Janeiro)
Using laser beams and colloids to probe the quantum vacuum

The quantum vacuum, the lowest-energy state of a quantum field, displays fluctuations which are closely connected with Heisenberg's uncertainty principle. Although the vacuum energy is infinite, it provides a general theoretical ground for the Casimir (usually attractive) interaction between neutral atoms or material surfaces, which includes the van der Waals interaction as the limit of short distances.

After a historical account of Casimir’s contribution, I review the theoretical and experimental progress in Casimir physics over the last decade. On the theoretical front, the scattering approach [1] now allows one to derive the Casimir interaction from the scattering matrices of the individual interacting bodies, opening the way for the derivation of exact results for a variety of non-trivial geometries, including those probed experimentally. By combining the scattering approach with state-of-the-art numerical methods, we have derived exact results for the plane-sphere geometry for the parameters corresponding to typical experiments [2], shedding new light on the role of dissipation in the Casimir interaction. We are currently probing the Casimir force between two colloidal microspheres with the help of single-beam optical traps, also known as optical tweezers [3]. The tunable stiffness of optical tweezers allows us to measure very weak forces, in the femtonewton range, opening the possibility of probing the Casimir interaction at longer distances. This should allow us to investigate the screening of the Casimir interaction by movable ions in solution.

[1] A. Lambrecht, P. A. Maia Neto, and S. Reynaud, New J. Phys. 8, 1 (2006).

[2] M. Hartmann, G.-L. Ingold and P. A. Maia Neto, Phys. Rev. Lett. 119, 043901 (2017).

[3] D. S. Ether Jr et al, EPL 112, 44001 (2015).