  Based on a simple model, we theoretically show that asymmetric transportation
is possible in nanoscale systems experiencing thermal noise without the
presence of external fluctuations. The key to this theoretical advance is that
the correlation lengths of the thermal fluctuations become significantly long
for nanoscale systems. This differs from macroscopic systems in which the
thermal noises are usually treated as white noise. Our observation does not
violate the second law of thermodynamics, since at nanoscale, extra energy is
required to keep the asymmetric structure against thermal fluctuations.
