Polaronic neutron in dilute alpha matter: A $p$-wave Bose polaron

TL;DR

This paper models a neutron in dilute alpha matter as a p-wave Bose polaron, revealing how medium density affects its effective mass and enabling dineutron formation, with implications for nuclear physics and astrophysics.

Contribution

It provides an analytical formula for the neutron's effective mass in alpha condensates and explores dineutron formation in medium, extending polaron theory to nuclear matter.

Findings

Effective mass increases with alpha density.

Dineutron can form in medium due to neutron-neutron attraction.

Analytical expression derived for polaron properties.

Abstract

We theoretically investigate quasiparticle properties of a neutron immersed in an alpha condensate, which is one of the possible states of dilute symmetric nuclear matter. The resonant $p$-wave neutron-alpha scattering, which plays a crucial role in forming halo nuclei, is considered. This system is similar to a Bose polaron near the $p$-wave Feshbach resonance that can be realized in cold-atomic experiments. Calculating the self-energy within the field-theoretical approach, we give an analytical formula for the effective mass of a polaronic neutron as a function of alpha condensation density. Moreover, two adjacent neutrons in a medium, each of which behaves like a stable polaron having an enhanced effective mass, can form a bound dineutron, with the help of $^1S_0$ neutron-neutron attraction. This is in contrast to the case of the vacuum, where a dineutron is known to be unbound. Our result would be useful for understanding many-body physics in astrophysical environments as well as the formation of multi-nucleon clusters in neutron-halo nuclei.