4 mois (Mars 2020 - Juin 2020)

Theoretical investigation of the properties of polar diatomic molecules


This proposal is devoted to the theoretical investigation of the properties of polar diatomic molecules comprising one alkali‐atom (A) and one lanthanide atom (La). Its central objective is the determination of ways to create such molecules in the ultracold regime (T<<1microkelvin), as the building block for a strongly‐correlated quantum system for quantum simulation, where synthetic dimensions could be implemented. Besides its novel and challenging aspect, this theoretical project discussed below has for primary goal to establish solid theoretical grounds to the development of a novel experimental setup, in a very promising field.Cold atom physics led, over the past decade, to major achievements on both fundamental understanding of quantum mechanics and new technological applications: the observation of the BCS‐BEC crossover or the development of atomic clocks used in several fields of research, are just some examples. Recent development of cold atom experiments now concern lanthanide species, such as Dy or Er.Ultracold polar molecules, due to their complex structure, large induced electric dipole moment, and thus long‐range anisotropic interactions, are also promising candidates to explore strongly‐interacting systems and exotic phases of matter as well as other emerging phenomena like, for instance, ultracold chemistry. Although far more challenging from a technical point‐of‐view, recent experimental developments led to a better control over both cooling and trapping of these particles, resulting in the first observation of a degenerate cloud of polar molecules.The choice of a lanthanide plus alkali‐metal atom, contrarily of two alkali‐metal atoms used in most polar molecules experiments, although challenging, offers several possibilities for quantum simulation. The molecule will naturally inherit from the large magnetic dipole moment of the lanthanide atom, thus resulting in a system with both large magnetic and electric dipole moments. This particularity would allow the molecule to be manipulated with both electromagnetic (light) and magnetic fields. The present proposalaims at investigating the electronic properties of polar diatomic molecules comprising one alkali‐atom (A) and dysprosium atom (Dy). The internship project will focus on the Investigation of the interactions between Dysprosium and alkali‐metal atoms at large distances R. The approach is based on the stationary second‐order perturbation theory. The interaction is written as a standard multipolar expansion, where for the ground‐state, the dominant term is the anisotropic van der Waals term varying as C6/R6. It is worth noting here that this formalism for the long‐range interaction indeed considers the high total angular momentum of Dy (J=8), resulting in a complex structure of the corresponding potential energy curves with possibly anisotropic C6 coefficients. The knowledge of these long‐range Dy‐A interactions is crucial for the future modeling of elastic collisions at ultralow energies, as well as of the possible excitation scheme of the diatomic complex.

Olivier DULIEU - Contacter
bât. 221, Campus D’Orsay, 91400 Orsay