Abstract
We investigate a mesoscopic spin current for strongly interacting Fermi gases through a quantum point contact. Under the situation where spin polarizations in left and right reservoirs are same in magnitude but opposite in sign, we calculate the contribution of quasiparticles to the current by means of the linear response theory and many-body $T$-matrix approximation. For a small spin-bias regime, the current in the vicinity of the superfluid transition temperature is strongly suppressed due to the formation of pseudogaps. For a large spin-bias regime where the gases become highly polarized, on the other hand, the current is affected by the enhancement of a minority density of states due to Fermi polarons. We also discuss the broadening of a quasiparticle peak associated with an attractive polaron at a large momentum, which is relevant to the enhancement.
Highlights
Quantum simulation with ultracold atomic gases allows one to explore regimes of quantum many-body problems where conventional systems such as condensed matter and nuclear matter are hard to reach [1,2,3]
To incorporate the polaronic properties in a correct fashion, we perform the finite-temperature many-body formalism of Fermi polarons. By using this formalism, we show that the crossover from the pseudogap to the polarons can be explored through spin transport
By looking at a small h regime, we show that the pseudogap effect can be captured with spin transport, which may be complementary to the tunneling spectroscopy in high-Tc superconductors [48]
Summary
Quantum simulation with ultracold atomic gases allows one to explore regimes of quantum many-body problems where conventional systems such as condensed matter and nuclear matter are hard to reach [1,2,3]. One of the most remarkable features resulting from a strong interaction is the formation of a pseudogap [19,20,21,22,23,24,25,26,27], where a dip structure in the single-particle density of states (DOS) in the normal phase near the transition temperature appears While this pseudogap phenomenon has indirectly been observed with photoemission spectroscopy [28,29,30], the measurement of thermodynamic quantities has showed a Fermi-liquid-like behavior and suggested the absence of the pseudogap near unitarity [31,32,33]. In order to study spin transport of two-terminal systems in normal Fermi gases with strong interaction, we begin with the following grand canonical Hamiltonian:.
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