Identification of Two Mechanisms for Current Production in a Biharmonic Flashing Electron Ratchet

Scientific Achievement

The current in a one-dimensional electron ratchet is controlled by the shape of the potential and the friction.

Significance and Impact

The basic relationships between the current and ratchet parameters are the first step to experimentally realizing electron ratchets for low-power, high-noise applications.

The ratchet current as a function of friction applied to the electron. The ‘friction’ is the ratio of the electron relaxation time, τ_relax, to the period of oscillation (lower is higher energy input), τ_ratchet. The plot is divided into weak (left) and strong (right) friction regimes, each with their own mechanism of current production and dependence on the shape of the ratchet potential.

Research Details

  • A ratchet drives the system away from equilibrium, without a bias, to extract current from fluctuations.
  • The current is the highest when the friction is low due to a resonance between the oscillation of the potential and the wavefunction. This resonance also leads to current reversals and regions of parameter space where there is no current.
  • The current is lower when friction is high (i.e. the potential oscillates slow relative to the electron relaxation), and is more tolerant to changes in shape.

Work performed at Northwestern University