  Photovoltaic effect of neutral atoms using inhomogeneous light in double-trap
opened system is studied theoretically. Using asymmetric external driving field
to replacing original asymmetric chemical potential of atoms, we create
polarization of atom population in the double-trap system. The polarization of
atom number distribution induces net current of atoms and works as collected
carriers in the cell. The cell can work even under partially coherent light.
The whole configuration is described by quantum master equation considering
weak tunneling between the system and its reservoirs at finite temperature. The
model of neutral atoms could be extended to more general quantum particles in
principle.
