Constructive role of non-adiabaticity for quantized charge pumping

Nonadiabatic Control of Geometric Pumping

We study nonadiabatic effects of geometric pumping. With arbitrary choices of periodic control parameters, we go beyond the adiabatic approximation to obtain the exact pumping current. We find that a geometrical interpretation for the nontrivial part of the current is possible even in the nonadiabatic regime. The exact result allows us to find a smooth connection between the adiabatic Berry phase theory at low frequencies and the Floquet theory at high frequencies. We also study how to control the geometric current. Using the method of shortcuts to adiabaticity with the aid of an assisting fie…

Nonadiabatic Correction and Adiabatic Criteria of Noninteracting Quantum Dot Systems

We theoretically study nonadiabatic corrections for charge pumping in a noninteracting electron model of a single-level quantum dot. We derive a formula for the velocity limit of parameter driving to realize adiabatic pumping and illustrate its features in the wide-band limit. We discuss the effect of the nonadiabatic corrections in terms of a typical velocity limit, which is defined by averaging the velocity limits on the parameter contour. We also show that the typical velocity limit vanishes when the adiabaticity breakdown occurs in a quantum dot coupled to reservoirs with a band edge.

Shortcuts to Adiabatic Pumping in Classical Stochastic Systems

Adiabatic pumping is characterized by a geometric contribution to the pumped charge, which can be non-zero even in the absence of a bias. However, as the driving speed is increased, non-adiabatic excitations gradually reduce the pumped charge, thereby limiting the maximal applicable driving frequencies. To circumvent this problem, we here extend the concept of shortcuts to adiabaticity to construct a control protocol which enables geometric pumping well beyond the adiabatic regime. Our protocol allows for an increase, by more than an order of magnitude, in the driving frequencies, and the meth…

原子尺度螺旋磁体中的电荷与自旋泵浦理论

Theory of charge and spin pumping in atomic-scale spiral magnets

该研究在微观量子模型下探究原子尺度螺旋磁体的电荷与自旋泵浦效应，揭示电荷电流与混合动量-相子贝里相位的关联及近量子化特性，还分析了非绝热性、接触类型和无序对输运的影响。

Fast and accurate Cooper pair pump

We propose a method to perform accurate and fast charge pumping in superconducting nanocircuits. Combining topological properties and quantum control techniques based on shortcuts to adiabaticity, we show that it is theoretically possible to achieve perfectly quantised charge pumping at any finite-speed driving. Model-specific errors may still arise due the difficulty of implementing the exact control. We thus assess this and other practical issues in a specific system comprised of three Josephson junctions. Using realistic system parameters, we show that our scheme can improve the pumping acc…

An ideal rapid-cycle Thouless pump

Thouless pumping is a fundamental instance of quantized transport, which is topologically protected. Although its theoretical importance, the adiabaticity condition is an obstacle for further practical applications. Here, focusing on the Rice-Mele model, we provide a family of finite-frequency examples that ensure both the absence of excitations and the perfect quantization of the pumped charge at the end of each cycle. This family, which contains an adiabatic protocol as a limiting case, is obtained through a mapping onto the zero curvature representation of the Euclidean sinh-Gordon equation…