AMO seminar 

Controlling photoassociation and magnetoassociation of ultracold molecules

with non-resonant light

Rosario González-Férez

University of Granada, Spain

Time: Thursday May 7, 15:15
Duration: 45 minutes
Place: Fysisk Auditorium
Coffee, tea and cake will be served at 15:01

Abstract

Photoassociation, assembling molecules from atoms using laser light, is limited by the low density of atom pairs at sufficiently short interatomic separations. In this talk, we suggest the use of nonresonant light to control shape resonances. The non-resonant light couples to the anisotropic polarizability of an atom pair, shifting the position of shape resonances to lower energies and increasing the resonances thermal weight in an ultracold trap. This leads to an enhancement of photoassociation rates by several orders of magnitude and opens the way to significantly larger numbers of ground-state molecules in a thermal ensemble than achieved so far [1]. Photoassociation relies only on the presence of optical transitions, which usually are abundant, the light-matter coupling via the anisotropic polarizability is of universal character and shape resonances are ubiquitous for diatomic molecules.

Magnetically tunable Feshbach resonances for polar paramagnetic ground-state diatomic molecules are too narrow to allow for magnetoassociation starting from trapped, ultracold atoms. In the second part of this talk, we show that non-resonant light, induces Feshbach resonances and modifies their position and width. This is due to the non-resonant light changing the background scattering length and altering the differential magnetic susceptibility. For non-resonant field intensities of the order of 10⁹ W/cm2, we find the width to be increased by 3 orders of magnitude, reaching a few Gauss, which are sufficient for magnetoassociation [2]. This opens the way for producing ultracold molecules with sizable electric and magnetic dipole moments and thus for many-body quantum simulations with

such particles.

[1] R. Gonzalez-Ferez and C. P. Koch, Phys. Rev. A 86, 063420 (2012)

[2] M. Tomza, R. Gonzalez-Ferez, C. P. Koch, and R. Moszynski, Phys. Rev. Lett. 112, 113201 (2014)

Michael Drewsen and Henrik Stapelfeldt