标题： 超越普通的声电效应：声学领域中的超光速现象和声子介导的布洛赫增益 显示英文标题

标题： Beyond the ordinary acoustoelectric effect: superluminal phenomena in the acoustic realm and phonon-mediated Bloch gain

摘要： 已被证明，相干声子可以作为一种强大的工具，用于控制和增强纳米结构材料的光电和输运特性。 最近的研究表明，在半导体异质结构中，声子与快速运动载流子的相互作用可能伴随着电子-声子不稳定性，这些不稳定性会导致普通和诱导的切连科夫效应。 然而，这种不稳定性的发展仍然知之甚少。 我们的研究显示，在由声平面波驱动的最小带半导体超晶格（SLs）中的非平衡电荷输运中，除了切连科夫不稳定性之外，还可能存在其他超音速现象。 使用半经典非微扰方法和分岔理论的一些元素，我们找到了由超音速电子发射特定SL声子及其对电子的反作用引起的动力学不稳定性（分岔）的条件。 值得注意的是，底层的辐射机制与正常或异常多普勒效应有关，这完全符合金兹堡-弗兰克-坦姆理论。 还讨论了诱导多普勒效应的出现，这与通过SL的空间周期性结构传播的电子束的形成有关。 当声波振幅超过一定阈值时，系统中发展起来的动力学不稳定性表现为漂移速度反转、声 attenuation 中的共振和绝对负迁移率。 我们证明，发现的超光速多普勒现象可用于可调宽带放大和生成GHz-THz电磁波，这为开发新型声子器件奠定了基础。 显示英文摘要

摘要： It has been shown that coherent phonons can be used as a potent tool for controlling and enhancing optoelectronic and transport properties of nanostructured materials. Recent studies revealed that interaction of acoustic phonons and fast-moving carriers in semiconductor heterostructures can be accompanied by electron-phonon instabilities that cause ordinary and induced Cherenkov effects. However, the development of such instabilities is still poorly understood. Our study shows that other supersonic phenomena, beyond the Cherenkov instability, are possible for non-equilibrium charge transport in the miniband semiconductor superlattices (SLs) driven by an acoustic plane wave. Using semiclassical nonperturbative methods and elements of the bifurcation theory, we find the conditions for the onset of dynamical instabilities (bifurcations) which are caused by the emission of specific SL phonons by supersonic electrons, and their back action on the electrons. Notably, the underlying radiation mechanism is connected either to normal or anomalous Doppler effects in full accordance with the Ginzburg-Frank-Tamm theory. The appearance of induced Doppler effects is also discussed in relation to the formation of electron bunches propagating through the spatially periodic structure of the SL. When the amplitude of the acoustic wave exceeds certain threshold, the dynamical instabilities developed in the system are manifested as drift velocity reversals, resonances in sound attenuation and absolute negative mobility. We demonstrate that the discovered superluminal Doppler phenomena can be utilized for tunable broadband amplification and generation of GHz-THz electromagnetic waves, which creates a ground for development of novel phononic devices.