利用声波在超晶格中诱导高频电流振荡
Using acoustic waves to induce high-frequency current oscillations in superlattices
摘要：
我们表明，GHz的声波在半导体超晶格中可以诱导太赫兹电子动力学，关键取决于波的振幅。在阈值幅度以下，声波以由静态电场产生的峰值漂移速度过冲（overshooting）拖拽电子通过超晶格。在这种情况下，单个电子执行具有太赫兹频率分量的漂移轨道。当波的振幅超过临界阈值时，布洛赫样振荡的突然发生导致负的微分速度。声波还通过引起局部电子积累和耗尽区域的形成来影响电子的集体行为，所述局部电子积累和耗尽区域传播通过超晶格，从而即使对于非常小的波幅也产生自持电流振荡。我们发现，潜在的单电子动力学，特别是声波拖曳和布洛赫振荡制度之间的过渡，强烈影响的电子的空间分布和电流振荡的形式。特别地，电流振荡的幅度非单调地依赖于声波的强度，反映了单电子漂移速度的变化。
英文摘要：
We show that GHz acoustic waves in semiconductor superlattices can induce THz electron dynamics that depend critically on the wave amplitude. Below a threshold amplitude, the acoustic wave drags electrons through the superlattice with a peak drift velocity overshooting that produced by a static electric field. In this regime, single electrons perform drifting orbits with THz frequency components. When the wave amplitude exceeds the critical threshold, an abrupt onset of Bloch-like oscillations causes negative differential velocity. The acoustic wave also affects the collective behavior of the electrons by causing the formation of localised electron accumulation and depletion regions, which propagate through the superlattice, thereby producing self-sustained current oscillations even for very small wave amplitudes. We show that the underlying single-electron dynamics, in particular the transition between the acoustic wave dragging and Bloch oscillation regimes, strongly influence the spatial distribution of the electrons and the form of the current oscillations. In particular, the amplitude of the current oscillations depends non-monotonically on the strength of the acoustic wave, reflecting the variation of the single-electron drift velocity.
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