Effective mass of free neutrons in neutron star crust

The inner layers of a neutron star crust, composed of a Coulomb lattice of neutron rich nuclear clusters immersed in a sea of “free” superfluid neutrons, are closely analogous to periodic condensed matter systems such as electronic, photonic or phononic crystals. Applying methods from solid state physics to the neutron star context, it has been recently shown that Bragg scattering leads to a strong renormalization of the neutron mass in the bottom layers of the crust. Knowledge of this effective mass throughout the crust is essential in order to understand the dynamical properties of the neutron superfluid and the origin of pulsar glitches. The purpose of the present work is to evaluate this effective mass in the outermost layers of the inner crust, near the drip point ρdrip∼4×1011 g cm−3. The results are compared with the case of electrons in ordinary solids and as an example the corresponding effective electron mass in copper is calculated.