Self-diffusion and structure of a quasi two-dimensional, classical Coulomb gas under increasing magnetic field and temperature

The influence of a magnetic field applied perpendicularly to the plane of a quasi two-dimensional, low-density classical Coulomb gas, with interparticle potential U(r)∼1/r, is studied using momentum-conserving dissipative particle dynamics simulations. The self-diffusion and structure of the gas are studied as functions of temperature and strength of the magnetic field. It is found that the gas undergoes a topological phase transition when the temperature is varied with, in accord with the Bohr-van Leeuwen (BvL) theorem, the structural properties being unaffected, resembling those of the strictly two-dimensional Kosterlitz-Thouless transition, with U(r)∼ln(r). Consistent with the BvL theorem, the transition temperature and the melting process of the condensed phase are unchanged by the field. Conversely, the self-diffusion coefficient of the gas is strongly reduced by the magnetic field. At the largest values of the cyclotron frequency, the self-diffusion coefficient is inversely proportional to the applied magnetic field. The implications of these results are discussed.