Nonequilibrium stationary states with ratchet effect

Area of Science:

• Statistical Mechanics
• Condensed Matter Physics
• Nonlinear Dynamics

Background:

• Particles in thermal equilibrium on lattices with asymmetric scatterers typically do not exhibit directed transport due to thermodynamic laws.
• Understanding particle dynamics under external fields is crucial for designing novel electronic devices.

Purpose of the Study:

• To investigate the possibility of inducing directed particle transport in a system with asymmetric scatterers.
• To explore the effect of a polarized monochromatic field on particle dynamics and flow.
• To theoretically estimate the directed current generated by a microwave field in semiconductor heterostructures.

Main Methods:

• Modeling particle dynamics using Nosè-Hoover dynamics on a triangular lattice with oriented semidisk elastic scatterers.
• Introducing a polarized zero-mean monochromatic field to observe its effect on particle movement.
• Developing a theoretical framework to estimate the directed current in an antidot superlattice.

Main Results:

• Directed transport is ruled out by the second law of thermodynamics in the absence of an external field, despite scatterer asymmetry.
• The application of a polarized monochromatic field successfully creates a directed stationary flow.
• The induced flow exhibits a nontrivial dependence on temperature and field parameters.

Conclusions:

• Asymmetric scatterers alone do not guarantee directed transport; external fields are necessary.
• A polarized microwave field can effectively induce and control directed particle flow in these systems.
• The findings provide a theoretical basis for microwave-field-induced currents in semiconductor superlattices.