 |
Center for Nonlinear Studies |
Beginning with the discovery of superconductivity one hundred years ago, there has been a tremendous effort to understand the phenomenon of dissipationless flow, that is, superfluidity in quantum systems. While experimentalists can cool Helium-4 below it's lambda-point (~2.17 K) and into a superfluid state, this system, to some extent, remains mysterious because of its very high densities and strong interactions. However, in 1995 experimentalists at JILA and MIT succeeded in cooling trapped, bosonic alkali atoms into highly degenerate, dilute Bose-Einstein condensates (BECs). These atomic BECs provide ideal systems for studying superfluidity and other properties of quantum degeneracy. Their interactions are highly tunable and they are well-described by relatively simple theoretical models. More recently, there has been a great effort put towards producing condensates of dipolar atoms and molecules. The dipole-dipole interaction is long-range and anisotropic, leading to many interesting properties in these systems, including a roton-maxon feature in the spectrum of elementary excitations (much like that found in superfluid Helium-4) despite existing in a dilute, gaseous state. In this talk, I will outline the basic theoretical methods that are used to study BECs and discuss how we overcome the difficulties presented by the dipole-dipole interaction in this many-body theory. Additionally, I will discuss the important role that the roton plays in ultracold dipolar gases, including how it can lead to structured ground states and have a profound effect on the superfluid properties of these systems.
Host: Chris Ticknor, T-1, 5-5649, cticknor@lanl.gov