Non-adiabatic quantized charge pumping with tunable-barrier quantum dots

Charge pumping is a transport mechanism of generating electric current in the absence of a bias voltage. The pumping current results from periodic external modulation of parameters controlling a nanostructure connected to source and drain leads. Of particular interest has been the quantized regime when the current varies in steps of $q_e f$ as function of control parameters, where $q_e$ is the electron charge and $f$ is the frequency of modulation. The adiabatic approach to quantized pumping relies on staying close to equilibrium during the modulation which has been explored extensively in the past in devices with tunnel barriers defined at the fabrication stage. In recent years, the focus of the field of precision quantized pumping has shifted towards a novel direction where non-adiabaticity is an essential element in the operation. The non-adiabatic approach focuses on understanding of charge capture and release between the leads and a periodically isolated region (a quantum dot). A crucial element of the scheme is the dynamical tunability of tunneling barriers with sufficiently wide dynamical range. Corresponding devices have been known since many years, but their potential for high precision pumping has only recently been recognized. In this report we review the recent progress in implementations, modelling and applications of non-adiabatic quantized charge pumping with tunable barrier quantum dots.