Experimental tunneling ratchets

Adiabatically rocked electron ratchets, defined by quantum confinement in semiconductor heterostructures, were experimentally studied in a regime where tunneling contributed to the particle flow. The rocking-induced electron flow reverses direction as a function of temperature. This result confirms a recent prediction of fundamentally different behavior of classical versus quantum ratchets. A wave-mechanical model reproduced the temperature-induced current reversal and provides an intuitive explanation.