Nanotube in a periodic potential: A conveyer belt for electrons

Keywords:
adiabatic charge pump, current quantization

Abstract:
We consider a carbon nanotube in the presence of an externally applied
periodic potential. We show that, as a function of gate voltage that controls electron density (counted from the half-filled pi-band), the electron states can become incompressible (locked) when the density is commensurate with the potential. Namely, excitation gaps in spectrum can open up when the number of electrons per potential period is either an integer, or a simple fraction. Gaps for the integer-density states open up due to the Bragg diffraction, whereas the fractional-density gaps arise solely due to electron interactions. With chemical potential in the gap, an adiabatically moving external periodic potential will generate quantized current, realizing the adiabatic charge pump. Semiclassically, the charge is transported by a moving potential wave in a conveyer-belt fashion. The presence of electron interactions opens up a possibility to pump a fractional number of electrons per cycle (equivalently, to pump at a fraction of the base frequency).
The unprecedented control on the charge transfer potentially achievable
in this setup can be a crucial ingredient in areas as diverse as engineering of nanoscale devices, quantum computing, and metrology.
[D.S. Novikov, Phys. Rev. Lett. 95, 066401 (2005)]

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Nanotech 2006 Conference Program Abstract