  In this work, we present a mechanism that, based on quantum-mechanical
principles, allows one to recover kinetic energy at the nanoscale. Our premise
is that very small mechanical excitations, such as those arising from sound
waves propagating through a nanoscale system or similar phenomena, can be quite
generally converted into useful electrical work by applying the same principles
behind conventional adiabatic quantum pumping. The proposal is potentially
useful for nanoscale vibrational energy harvesting where it can have several
advantages. The most important one is that it avoids the use of classical
rectification mechanisms as it is based on what we call geometric
rectification. We show that this geometric rectification results from applying
appropriate but quite general initial conditions to damped harmonic systems
coupled to electronic reservoirs. We analyze an analytically solvable example
consisting of a wire suspended over permanent charges where we find the
condition for maximizing the pumped charge. We also studied the effects of
coupling the system to a capacitor including the effect of current-induced
forces and analyzing the steady-state voltage of operation. Finally, we show
how quantum effects can be used to boost the performance of the proposed
device.
