Christian Trefzger, Yvan Castin
We study the problem of a mobile impurity of mass $M$ interacting {\sl via} a s-wave broad or narrow Feshbach resonance with a Fermi sea of particles of mass $m$. Truncating the Hilbert space to at most one pair of particle-hole excitations of the Fermi sea, we determine ground state properties of the polaronic branch other than its energy, namely the polaron quasiparticle residue $Z$, and the impurity-to-fermion pair correlation function $G(\xx)$. We show that $G(\xx)$ deviates from unity at large distances as $-(A_4+B_4 \cos 2 \kf x)/(\kf x)^4$, where $\kf$ is the Fermi momentum; since $A_4>0$ and $B_4>0$, the polaron has a diverging rms radius and exhibits Friedel-like oscillations. In the weakly attractive limit, we obtain analytical results, that in particular detect the failure of the Hilbert space truncation for a diverging mass impurity, as expected from Anderson orthogonality catastrophe; at distances between $\sim 1/\kf$ and the asymptotic distance where the $1/x^4$ law applies, they reveal that $G(\xx)$ exhibits an intriguing multiscale structure.
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http://arxiv.org/abs/1210.8179
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