Hamiltonian ratchet of conventional pure quasi-2D electron system

TL;DR

This paper explores how conventional quasi-2D electron systems in semiconductors can act as quantum ratchets, generating directed currents from zero-mean oscillating electric fields through two distinct microscopic mechanisms.

Contribution

It introduces and analyzes two novel microscopic mechanisms—effective-mass swap and skin-effect ratchets—for quantum ratchet behavior in quasi-2D electron systems.

Findings

Effective-mass swap ratchet modulates mobility to produce directed current.

Skin-effect ratchet modulates electric field strength to generate currents.

Both mechanisms can produce linear and circular photocurrents.

Abstract

We trace a simple mechanical model of a ratchet, and embed its setup in a conventional quasi-two-dimensional electron system in a semiconductor heterostructure. Expressed are two distinct microscopic mechanisms for such systems to serve as quantum ratchets producing the in-plane directed current from zero-mean time-dependent electric fields. The effective-mass swap ratchet is based on modulation of the mobility through alteration of the electron's effective mass. Modulation of the strength of the effective in-plane electric field marks the skin-effect ratchet. They can generate both linear and circular photocurrents, the later taking place in the dissipationless regime.