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arXiv 1801.01650cond-mat.mes-hall
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交流驱动量子导体中的准粒子态:散射理论方法

Quasiparticle states in AC-driven quantum conductors: A scattering theory approach

Y. Yin

摘要:

本文介绍了一种提取交流驱动量子导体中准粒子波函数的一般方法。通过将布洛赫-弥赛亚约化引入到量子输运的散射理论中,我们从散射矩阵中构造了多体态,在多体态中可以提取准粒子的波函数.我们发现在费米海中可以激发出两种准粒子,而这两种准粒子都是粒子态和空穴态的叠加。由于电子数守恒,准粒子总是成对产生,导致量子导体中的粒子-空穴对激发。我们应用我们的方法来比较这些粒子-空穴对激发在完全透明的量子接触和介观电容器与单能级量子点。对于量子接触,可以激发多个对,而每个对的激发概率随着驱动场强度的增加而增加。粒子(空穴)分量总是与驱动场同相(180度异相)。这些特征与通过扩展的Keldysh-Green函数技术得到的结果一致。对于介观电容器,只有一个粒子-空穴对可以被激发,而相应的激发概率经历一个振荡的驱动场的强度增加。粒子(空穴)分量与驱动场之间存在非零相位延迟,该相位延迟可以通过介观电容中的点-引线耦合进行调谐。这些特征与量子接触的情况非常不同,量子接触可以归因于电子在介观电容器中的有限停留时间。我们还发现,我们的方法也可以提供一种从Wigner函数中提取准粒子波函数的通用方法,这对电子量子光学相关实验的信号处理有一定的帮助。

英文摘要:

We introduce a general procedure to extract the wave function of quasiparticles in AC-driven quantum conductors. By incorporating the Bloch-Messiah reduction into the scattering theory approach to quantum transport, we construct the many-body state from the scattering matrix, within which the wave function of quasiparticles can be extracted. We find that two kinds of quasiparticles can be excited, while both of them are superpositions of particle and hole states in the Fermi sea. Due to the electron number conservation, the quasiparticles are always created in pairs, resulting in particle-hole pair excitations in quantum conductors. We apply our approach to compare these particle-hole pairs excited in perfectly transparent quantum contacts and mesoscopic capacitors with single-level quantum dot. For the quantum contacts, multiple pairs can be excited, while the excitation probability of each pair increases as the strength of the driving field increasing. The particle(hole) components are always in phase (180 degrees out of phase) with the driving field. These features agree with the results obtained via the extended Keldysh-Green's function technique. For the mesoscopic capacitors, only one particle-hole pair can be excited, while the corresponding excitation probability undergoes an oscillation as the strength of the driving field increasing. A nonzero phase delay between the particle(hole) component and the driving field exists, which can be tuned via the dot-lead coupling in the mesoscopic capacitor. These features are very distinct from the case of quantum contacts, which can be attributed to the finite dwell time of electrons in the mesoscopic capacitor. We also find that our approach can also offer a general way to extract the wave function of quasiparticles from the Wigner function, making it helpful for the signal processing of relevant experiments in electron quantum optics.

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