Fermi polaron in low-density spin-polarized neutron matter

Abstract

We study the properties of a spin-down neutron impurity immersed in a low-density free Fermi gas of spin-up neutrons. In particular, we analyze its energy ($E_{\downarrow }$), effective mass ($m_{\downarrow }^{\ast }$) and quasiparticle residue ($Z_{\downarrow }$). Results are compared with those of state-of-the-art quantum Monte Carlo calculations of the attractive Fermi polaron realized in ultracold atomic gases experiments, and with those of previous studies of the neutron polaron. Calculations are performed within the Brueckner--Hartree--Fock approach using the chiral two-body nucleon-nucleon interaction of Entem and Machleidt at N${}^3$LO with a 500 MeV cut-off and the Argonne V18 phenomenological potential. Only contributions from the ${}^1{S}_0$ partial wave, which is the dominant one in the low-density region considered, are included. Contributions from three-nucleon forces are expected to be irrelevant at these densities and, therefore, are neglected in the calculation. Our results show that for Fermi momenta between $\sim 0.25$ and $\sim 0.45$ fm${}^{-1}$ the energy, effective mass and quasiparticle residue of the impurity vary only slightly, respectively, in the ranges $-0.604E_F<E_{\downarrow }<-0.635E_F$, $1.300m<m_{\downarrow }^{\ast }<1.085m$ and $0.741<Z_{\downarrow }<0.836$ in the case of the chiral interaction, and $-0.621E_F<E_{\downarrow }<-0.643E_F$, $1.310m<m_{\downarrow }^{\ast }<1.089m$ and $0.739<Z_{\downarrow }<0.832$ when using the Argonne V18 potential. These results are compatible with those derived from ultracold atoms and show that a spin-down neutron impurity in a free Fermi gas of spin-up neutrons with a Fermi momentum in the range $0.25\lesssim k_F\lesssim 0.45$ fm${}^{-1}$ exhibits properties very similar to those of an attractive Fermi polaron in the unitary limit.

6 pages, 2 figures. Accepted for publication as a Letter in Physical Review C

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• Polaron Problems in Ultracold Atoms: Role of a Fermi Sea across Different Spatial Dimensions and Quantum Fluctuations of a Bose Medium
• Finite-range effects in the unitary Fermi polaron
• Intersections of ultracold atomic polarons and nuclear clusters: How is a chart of nuclides modified in dilute neutron matter?
• Polaronic Proton and Diproton Clustering in Neutron-Rich Matter
• Exploring ${}^3{P}_0$ Superfluid in Dilute Spin-Polarized Neutron Matter
• Functional renormalisation group approach to the finite-temperature Bose polaron
• Polaronic neutron in dilute alpha matter: A $p$-wave Bose polaron
• The Gor'kov and Melik-Barkhudarov correction to an imbalanced Fermi gas in the presence of impurities
• Ab initio study of the neutron and Fermi polarons on the lattice