Heavy-Atom Tunneling

Sarina R. Chaiken, Elianna Frank, Keaton L. Mertz +1 more

Kaoru Awaka, Gen Tatara, Hidetoshi Fukuyama

K. Ziegler

A mixture of light and heavy fermionic atoms in an optical lattice is considered. Tunneling of the heavy atoms is neglected such that they are only subject to thermal fluctuations. There is a complex interplay between light and heavy atoms which results in an Ising-like distribution of heavy atoms with a first-order transition from homogeneous to staggered order. A second-order transition is possible between an ordered and a disordered phase of heavy atoms. Depending on the phase of heavy atoms, light atoms are scattered around and can propagate, diffuse, and localize. Due to correlations in the disordered phase of heavy atoms, there can be a gap in the spectrum of light atoms, leading to a Mottlike incompressible state.

K. Ziegler

A mixture of heavy atoms in a Mott state and light spin-1/2 fermionic atoms is studied in an optical lattice. Inelastic scattering processes between the two atomic species excite the heavy atoms and renormalize the tunneling rate as well as the interaction of the light atoms. An effective Hamiltonian for the latter is derived that describes tunneling of single fermions, tunneling of fermionic pairs, and an exchange of fermionic spins. Low-energy states of this Hamiltonian are a N\'eel state for strong effective repulsion, dimer states for moderate interaction, and a density wave of paired fermions for strong effective attraction.