Experiments

Two-component bose gases

The physics of multi-component gases is very rich due to the possibility of vector order parameters and the presence of different zero-temperature phases. In the cold gases context the ability to tune and to engineer single- and two-body properties permits many implementations of the physics of multi-component gases. The cold-gases toolbox allows to address very different and interesting phenomena like Andreev-Bashkin effect, (internal) Josephson effect, spin textures, quantum magnetism or the most recent field of non-abelian gauges, just to cite a few of them.

In our research, we are considering the easiest implementations, namely a 2- component (spinor) Bose gas.
The activity can be divided in two subfields, namely when the relative atom number is preserved and when an external field that drives the population transfer (spin-flipping) between the two atomic levels is present. The earlier case shows an interesting phenomenology related to the polaron physics and the supercurrent stability. The latter, where the spin excitations are generally gapped, show interesting properties related to quantum magnetism, to the topological excitations and to spin-orbit coupling.

We study the static and the dynamics of the gas, with and without optical lattice. The latter make the system equivalent to coupled Bose-Hubbard models.

Dynamical instability for counter current flow in a 2 component Bose-Einstein condensate in a toroidal trap.

Sketch of 2-component Bose gas with coherent coupling in an optical lattice