Strongly Interacting Quantum Mixtures of Ultracold Atoms

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

Electrons run our modern world: They zip through our light bulbs, smart phones, laptops, and TV screens. But remarkably, we do not understand fundamentally how they work together. We know electrons obey the rules of quantum mechanics: They can propagate as waves rather than billiard balls, and a fundamental principle forbids two of them to be in one and the same wave. But if we understood how an entire collection of electrons behaved in general, we could design materials that carry electricity without any loss. Laptops and smart phones would not heat up, we would not waste energy that could run entire countries just to transmit power between cities, and on an even more fundamental level we would understand the fabric of matter itself. This present project is designed to address these very points. The project will use atoms as stand-ins for electrons and other elementary particles to search for novel collective states of matter. In particular, the project aims to uncover the rules by which loss-less transport can occur in general settings, including superfluid states of matter - where atoms flow without friction - and novel states of collective flow in the presence of high magnetic fields. The present project will perform precision studies of the thermodynamics, collective excitations and transport properties of strongly interacting mixtures of bosons (Na) and fermions (40K and 6Li), with the goal of uncovering novel states of fermionic matter: From boson-induced superfluidity, inhomogeneous superfluidity in spin-imbalanced mixtures, to quantum Hall states of fermions and bosonic molecules. Feshbach scattering resonances will be used to tune interparticle interactions, and optical box potentials will be employed to realize homogeneous densities. Transport of spin, sound and heat will be performed using novel detection methods, e.g. the propagation of heat will be directly imaged. In-situ observations of excitations such as vortices and solitons will allow investigation of their stability as a function of species composition and effective magnetic fields. Comparisons to theoretical calculations, where they exist, will be made, which should advance our understanding of strongly interacting Fermi systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.