Theory Seminar: Identifying the trap loss mechanism in ultracold diatomic gases

Arthur Christianen (Radboud University, Nijmegen)
Ultracold dipolar gases have many applications such as quantum computation/simulation, controlled chemistry, and high precision measurements to challenge the standard model

Arthur Christianen (Radboud University, Nijmegen)
Herbert-Walther Lecture Hall G0.25
Wed 12. Juni 2019, 11:30 am (MEZ)

Abstract:

    Ultracold dipolar gases have many applications such as quantum computation/simulation, controlled chemistry, and high precision measurements to challenge the standard model. The experimentally realized coherence time in these gases is approaching the second (for NaK) and is now limited by the trapping time of the molecules. The loss mechanism limiting this trapping time is not yet understood and the loss rate is unexpectedly high, since nonreactive molecules disappear from the trap with a rate as if they were reactive. The hypothesis in the field is that the loss is caused by "sticky collisions", i.e., that molecules stick together when they collide for times in the order of milliseconds to seconds. In this time, the collision complexes themselves may leave the trap or a third molecule may collide with the complex, resulting in the loss of both collision partners.

    In our work we show that the actual sticking times of the molecules are three orders of magnitude smaller than previously estimated and that the previously suggested loss mechanisms can therefore not explain the experimental observations. We construct a realistic potential energy surface for NaK-NaK collisions and we study the dynamics of the complexes quasiclassically and statistically. We find that trapping laser excitation of the collision complexes is the most likely cause of the experimental losses. We propose that the losses may be strongly suppressed by changing the wavelength of the trapping lasers from 1064 nm to 10 micron.

    Reference: arXiv:1905.06846