Observation of spin-space quantum transport induced by an atomic quantum point contact

Samuel Häusler, Martin Lebrat, Dominik Husmann +5 more

Kiyotaka Ono, Toshiya Higomoto, Yugo Saito +3 more

Quantum transport is ubiquitous in physics. So far, quantum transport between terminals has been extensively studied in solid state systems from the fundamental point of views such as the quantized conductance to the applications to quantum devices. Recent works have demonstrated a cold-atom analog of a mesoscopic conductor by engineering a narrow conducting channel with optical potentials, which opens the door for a wealth of research of atomtronics emulating mesoscopic electronic devices and beyond. Here we realize an alternative scheme of the quantum transport experiment with ytterbium atoms in a two-orbital optical lattice system. Our system consists of a multi-component Fermi gas and a localized impurity, where the current can be created in the spin space by introducing the spin-dependent interaction with the impurity. We demonstrate a rich variety of localized-impurity-induced quantum transports, which paves the way for atomtronics exploiting spin degrees of freedom.

Xiaoyu Dai, Boyang Liu

The particle and spin transports through a quantum point contact between two Fermi gases with Raman-induced spin-orbit coupling are investigated. We show that the particle and spin conductances both demonstrate the structure of plateaus due to the mesoscopic scale of the quantum point contact. Compared with that of normal Fermi gases, the height of the plateau of the particle conductance is enhanced by the spin-orbit-coupling effect for the whole parameter space. This implies that the 0.7 anomaly observed in mesoscopic experiments is unlikely to be induced purely by the spin-orbit coupling. Furthermore, the generation of spin current is investigated in this system. We find that the spin current can be induced by only the bias of the spin difference between the two reservoirs for the case of vanishing two-photon detuning. When the two-photon detuning is nonzero, the spin current can also be generated by the bias of the total particle number between the two reservoirs.

Francisco Mireles, Leo Diago Cisneros

Senz, Volkmar

Meng-Zi Huang, Jeffrey Mohan, Anne-Maria Visuri +6 more

We measure superfluid transport of strongly interacting fermionic lithium atoms through a quantum point contact with local, spin-dependent particle loss. We observe that the characteristic non-Ohmic superfluid transport enabled by high-order multiple Andreev reflections transitions into an excess Ohmic current as the dissipation strength exceeds the superfluid gap. We develop a model with mean-field reservoirs connected via tunneling to a dissipative site. Our calculations in the Keldysh formalism reproduce the observed nonequilibrium particle current, yet do not fully explain the observed loss rate or spin current.