Anomalous conductance of a strongly interacting Fermi gas through a quantum point contact

Abstract

In this work we study the particle conductance of a strongly interacting Fermi gas through a quantum point contact. With an atom-molecule two-channel model, we compute the contribution to particle conductance by both the fermionic atoms and the bosonic molecules using the Keldysh formalism. Focusing on the regime above the Fermi superfluid transition temperature, we find that the fermionic contribution to the conductance is reduced by interaction compared with the quantized value for the non-interacting case; while the bosonic contribution to the conductance exhibits a plateau with non-universal values that is larger than the quantized conductance. This feature is particularly profound at temperature close to the superfluid transition. We emphasize that the enhanced conductance arises because of the bosonic nature of closed channel molecules and the low-dimensionality of the quantum point contact.

Universal Spin Transport and Quantum Bounds for Unitary Fermions

“…At low temperature the attractive Fermi gas enters a superfluid (SF) phase. Mesoscopic transport experiments with near-unitary ultracold SF have observed suppression of spin conductance, consistent with a spin insulator (86)(87)(88)(89). The low-energy phonon excitations of the superfluid are responsible for particle and mass transport, while spin transport occurs exclusively via thermal fermionic excitations.…”

Band and Correlated Insulators of Cold Fermions in a Mesoscopic Lattice

“…The positions of the local extrema are shifted towards lower V g as attractive interactions are increased, which is consistent with an increase of the atom density at the center of the cloud when approaching unitarity. The persistence of local extrema is very surprising considering the dramatic consequences of attractive interactions on transport in an atomic quantum wire, both experimentally observed and theoretically expected in the absence of a lattice [14,[22][23][24].…”

Particle and spin transports of spin-orbit coupled Fermi gas through a Quantum Point Contact

“…Many experiments have been conducted, including particle transport [1][2][3][4][5][6][7][8][9], spin transport [10][11][12][13][14] and heat transport [15][16][17]. Particularly, the realization of two-terminal set-up by ETH's group [1, 2, 4-6, 15, 16] paved a road to extend this paradigmatic tool from condensed matter physics to various unique states in cold atom physics, for instance, the quantized conductance of neutral matter has been observed [2], and the anomalous conductance of unitary Fermi gas has been studied both experimentally [5] and theoretically [18][19][20].…”