绝热量子泵浦的参数优化

Optimal Driving Parameters of Adiabatic Quantum Pumping

摘要: 量子泵浦是在无偏压的输运器件中通过调控系统参数随时间周期性变化而产生直流电流的物理过程。根据绝热量子泵浦理论，计算散射矩阵元及其对调控参数的导数在参数空间的面积分可以简单地得到泵浦过程的直流电流或泵浦电量。本文针对一维含时缓变双势垒驱动的量子泵浦模型，采用Berry曲率函数具体计算了不同的系统参数对泵浦电流大小取值的影响。以双参数线性驱动和简谐驱动为例，得到了产生最大泵浦电流的参数变化形式。另外，我们采用的理论方法既可以统一地处理多光子吸收和发射过程，又可以完全包涵泵浦电流随双势垒驱动参数相位差变化的所有高阶谐波项，加深对量子泵浦过程的非简谐效应的认识。

Abstract: The quantum pump phenomenon is that a dc current can be generated at zero bias in the transport device through regulation of system parameters that change periodically with time. According to the adiabatic quantum pump theory, the quantum pumping process of dc current or pump power can be got by using the area integral of the scattering matrix derivatives to the control parameters in the parameter space. In the present work, the quantum pump through a one-dimensional system with time-dependent double-δ-barrier potentials is considered. By introducing the Berry cur-vature function, we calculated the influence of the different system parameters to the pump current. Taking two linear and harmonic drivers as two examples, we achieved the parameter variation pattern to generate maximum pump current. In addition, our theoretical approach not only can analysis one-photon and multi-photon absorption and emission proc- esses within one framework, but also can be completely inclusion the higher order harmonics terms of pumped current as a function of the driving phase difference in double barrier, i.e. the anharmonic effects of quantum pump, are totally included in the parameter space integral.