Field-modulated electronic specific heat of armchair graphene nanoribbons

Electronic properties and electronic specific heat of armchair graphene nanoribbons under perpendicular magnetic and parallel electric fields are studied by the tight-binding model. With increasing magnetic field, energy-gap is reduced and flatter band-edge state leads to an enhancement in the density of states. As electric field increases, energy-gap declines to zero and oscillatory energy dispersion causes rich variations in the density of states. Furthermore, field-modulated electronic properties strongly depends on ribbon's geometry. Specific heat, at zero field, increases with ribbon's width at low temperature; however, it shows an opposite behavior beyond critical temperature. The reduced energy-gap caused by magnetic field lowers threshold temperature inducing specific heat. Specific heat is enhanced or reduced with magnetic field that is dominated by critical temperature and profoundly related to ribbon's geometry. Low-temperature specific heat oscillates due to distorted energy dispersions induced by electric field that is enhanced by extra magnetic field. The increment of specific heat with electric field is larger than that with magnetic field, except at very low temperature.