Thermopower and conductance for a graphene p-n junction

The thermopower and conductance in a zigzag graphene p-n junction are studied by using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian. Our results show that the conductance and thermopower of the junction can be modulated by its width, the potential drop, and the applied perpendicular magnetic fields. A narrow graphene p-n junction shows insulating characteristics, and its thermopower is much larger than that of the wider one around the Dirac point. The insulating characteristic of the junction decreases as the width increases. In particular, with increasing junction width or the potential drop, the first conductance plateau is strongly enhanced and the thermopower is inverted around the Dirac point. A perpendicular magnetic field strongly suppresses the conductance and enhances the thermopower in the p-n region. The influence of edge vacancy defects on the conductance and thermopower is also discussed. Our results provide theoretical references for modulating the electronic and thermal properties of a graphene p-n junction by tuning its geometry and working conditions.