Adiabatic Charge Pump in a Y-shaped Zigzag Graphene Nanoribbon Junction

The adiabatic charge transport was theoretically studied in a Y-shaped zigzag graphene nanoribbon (ZGNR) junction with three time-dependent pumping potentials. By employing the Keldysh Green's function method, we found that a non-zero charge current can be pumped out in the device at a zero external bias owing to the single photon-assisted tunneling process. The pumped charge and its direction can be easily and efficently modulated by the quantum pump parameters such as the pumping frequency, the pumping phase, and the Fermi level. The Y-shaped spatial structure was also found to have little influence on the pumped current when the two pumping potentials are considered equal, which is similar to the two-terminal straight ZGNR charge pump. Our findings might be helpful to control the electrons in graphene pumping devices.