Hamiltonian ratchet of conventional pure quasi-2D electron system

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.