Coulomb crystals in the magnetic field

Abstract

The body-centered-cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic-field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields B > or approximately equal 10(14) G ). The effect of the magnetic field on ion displacements in a strongly magnetized neutron star crust can suppress the nuclear reaction rates and make them extremely sensitive to the magnetic-field direction.

Neutron Stars—Cooling and Transport

“…The right panel of Fig. 7 illustrates the effects of a superstrong field on c v,i for the model of a harmonic Coulomb crystal (Baiko 2009). Here we plot the thermal phonon contribution to the heat capacity of the bcc Coulomb lattice calculated as the derivative c v = T ∂ S/∂ T of the fit to the phonon entropy S given by Eq.…”

Properties of the outer crust of strongly magnetized neutron stars from Hartree-Fock-Bogoliubov atomic mass models

“…According to the Bohr-van Leeuwen theorem [38], the lattice energy density is not affected by the magnetic field (we neglect here the small contribution due to the quantum zero-point motion of ions [39]). For point-like ions arranged in a body centered cubic lattice, the lattice energy density is approximately given by [40] …”

Spin dephasing as a probe of mode temperature, motional state distributions, and heating rates in a two-dimensional ion crystal

“…In quantum information science, where trapped-ion crystals provide a promising platform for quantum computation and simulation [4][5][6][7][8], the residual motion of the trapped ions produces infidelities that require careful evaluation. In plasma physics, trapped-ion crystals provide a convenient laboratory platform for studies of strongly coupled plasmas, which model dense astrophysical matter [9][10][11][12]. Careful measurements of ion motion are used to determine the ion energy and the plasma coupling.…”