Controlling thermoelectric transport and dissipation effects in superfluid transport in an atomic transport experiment*

We report on the control of the thermoelectric transport properties of a strongly interacting Fermi gas flowing through a quasi-two-dimensional contact and the effects of dissipation on non-linear superfluid transport through a quantum point contact (QPC). The versatility of cold-atom techniques allows us to precisely define a QPC using light potentials, to directly measure particle, heat and spin currents and to tune interatomic interactions. In a first experiment, we probe the thermoelectric effects induced by a temperature difference across a two-dimensional channel. We use an attractive as well as a repulsive gate to change the relative strength of channel and reservoir contributions to the thermoelectric transport. This allows us to tune the particle transport going from hot to cold to going from cold to hot. We find that strong interactions reduce the Seebeck coefficient of the channel which we attribute to hydrodynamic effects and resulting superfluid correlations inside the channel. In a second experiment, we locally dissipate a single spin state inside the QPC using an optical tweezer. We find that the dissipation has a strong effect on the nonlinear transport behavior of the superfluid transport making it linear. We also report on Keldysh theory calculations of the superfluid transport behavior with dissipation and compare them with our experimental results. These results open the way to the quantum simulation of the coupling between spin, heat and particle currents with cold atoms.