# CQD Special Seminar

### 27. July 2017 11:15

Konferenzraum 1, Physikalisches Institut, INF 226### Study of van der Waals and dipole-dipole interactions between Rydberg atoms via measurement of atom-pair kinetics

**Dr. Nithiwadee Thaicharoen**

Physikalisches Institut, Universität Heidelberg

The strong interactions between Rydberg excitations can result in spatial correlations between the excitations. In this work, I investigate how the character of the Rydberg-Rydberg interactions affects the nature of the spatial correlations and the evolution of those correlations in time. I use direct imaging of the center-of-mass positions of the individual Rydberg atoms and pair-correlation analysis to observe the atom-pair kinetics due to binary dipolar forces. In the first experiment, atoms are excited to a Rydberg state that experiences a repulsive van der Waals interaction. The Rydberg excitations are prepared with a well-defined initial separation, and the effect of van der Waals forces is observed by tracking the interatomic distance between the Rydberg atoms. The atom trajectories and thereby the interaction coefficient C6 are extracted from the pair correlation functions of the Rydberg atom positions. In the second experiment, the Rydberg atoms are prepared in a highly dipolar state by using adiabatic state transformation. The atom-pair kinetics that follow from the strong dipole-dipole interactions are observed. The pair correlation results provide the first direct visualization of the electric-dipole interaction and clearly exhibit its anisotropic nature. The observation also shows the dynamics reminiscent of disorder-induced heating in strongly coupled particle systems.

**References**

[1] N. Thaicharoen, A. Schwarzkopf, and G. Raithel, Phys. Rev. A **92**, 040701(R) (2015)

[2] N. Thaicharoen, L.F. Gonçalves, G. Raithel, Phys. Rev. Lett. **116**, 213002 (2016)

[3] L. F. Gonçalves, N. Thaicharoen, and G. Raithel, J. Phys. B: At. Mol. Opt. Phys. **49**, 154005 (2016)

Finite temperature simulations of false vacuum decay in a spin-1 Bose gas

*Dr. Kate Brown, School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, UK*, Physikalisches Institut, INF 226, K 1-3