  We report a theoretical study of electron transport along helical molecules
under an external electric field, which is perpendicular to the helix axis of
the molecule. Our results reveal that the topological states could appear in
single-helical molecule and double-stranded DNA in the presence of the
perpendicular electric field. And these topological states guarantee adiabatic
charge pumping across the helical molecules by rotating the electric field in
the transverse plane and the pumped current at zero bias voltage is quantized.
In addition, the quantized current constitutes multiple plateaus by scanning
the Fermi energy as well as the bias voltage, and hold for various model
parameters, since they are topologically protected against perturbations. These
results could motivate further experimental and theoretical studies in the
electron transport through helical molecules, and pave the way to detect
topological states and quantized current in the biological systems.
