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arXiv:1503.05454 · Physical Review B

Signatures of pairing and spin-orbit coupling in correlation functions of Fermi gases

Chien‐Te Wu, Brandon Anderson, Rufus Boyack, Kathryn Levin

Published Jun 17, 2015• 9 citations
arXivHTMLPDF

Abstract

We derive expressions for density-density and spin-spin correlation functions in the (greatly enhanced) pseudogap phase of spin-orbit-coupled Fermi gases. Density-density correlation functions are found to be relatively insensitive to the presence of these Rashba spin-orbit effects. To arrive at spin-spin correlation functions we derive new $f$-sum rules, valid even in the absence of a spin conservation law. Our spin-spin correlation functions are shown to be fully consistent with these $f$-sum rules. Importantly, they provide a clear signature of the Rashba band structure and separately help to establish the presence of a pseudogap.

DOI
10.1103/physrevb.91.220504

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We investigate normal-state properties of spin-orbit-coupled Fermi gases with repulsive sss-wave interaction, in the absence of molecule formation, i.e., in the so-called ``upper branch.'' Within the framework of random-phase approximation, we derive analytical expressions for the quasiparticle lifetime ${\ensuremath{\tau}}_{s}$, the effective mass ms∗{m}_{s}^{*}ms∗​, and the Green's function renormalization factor Zs{Z}_{s}Zs​ in the presence of Rashba spin-orbit coupling. In contrast to spin-orbit-coupled electron gas with Coulomb interaction, we show that the modifications are dependent on the Rashba band index sss and occur in the first order of the spin-orbit-coupling strength. We also calculate experimental observables such as spectral weight, density of state, and specific heat, which exhibit significant differences from their counterparts without spin-orbit coupling. We expect our microscopic calculations of these Fermi-liquid parameters would have immediate applications to the spin-orbit-coupled Fermi gases in the upper branch of the energy spectrum.
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We investigate theoretically BEC-BCS crossover physics in the presence of Rashba spin-orbit coupling in a system of a two-component Fermi gas with and without a Zeeman field that breaks the population balance between the two components. A bound state (Rashba pair) emerges because of the spin-orbit interaction. We study the properties of Rashba pairs using standard pair fluctuation theory. At zero temperature, the Rashba pairs condense into a macroscopic mixed-spin state. We discuss in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment.
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