Real-time observation of interfering crystal electrons in high-harmonic generation
Real-time observation of interfering crystal electrons in high-harmonic generation
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DOI：
10.1038/nature14652
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发表时间：
2015-07-30
期刊：
影响因子：
64.8
通讯作者：
Huber, R.
中科院分区：
文献类型：
--
作者：
Hohenleutner, M.;Langer, F.;Huber, R.
粒子的加速和碰撞一直是探索物质结构的关键策略。强光波可以控制和重新碰撞电子波包，产生高次谐波辐射，对原子和分子的结构和动力学进行编码，并为阿秒科学奠定基础(1-3)。最近发现的散装固体中的高次谐波产生(4-6)将超快加速的思想与复杂的凝聚态物质系统相结合，并为紧凑型固态阿秒源(6-8)和光频率电子学(3,5,9,10)带来了希望。然而，潜在的量子运动迄今为止还无法实时观察到。在这里，我们直接在时域中研究块体固体中高次谐波的产生，并揭示了晶体中一种新型的强场激发。与已建立的原子源（1-3,9,11）不同，我们的固体以一系列子周期爆发的形式发射高次谐波辐射，这些子周期爆发在时间上与驱动太赫兹波形的一个极性的场峰一致。我们证明这些特征是涉及来自多个价带的电子的非微扰量子干涉过程的特征。这些结果确定了未来固态阿秒源和下一代光波电子学的关键机制。新的量子干涉过程证明了全光能带结构重建的希望，并为光时钟速率下可能的量子逻辑操作奠定了基础。
Acceleration and collision of particles has been a key strategy for exploring the texture of matter. Strong light waves can control and recollide electronic wavepackets, generating high-harmonic radiation that encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science(1-3). The recent discovery of high-harmonic generation in bulk solids(4-6) combines the idea of ultrafast acceleration with complex condensed matter systems, and provides hope for compact solid-state attosecond sources(6-8) and electronics at optical frequencies(3,5,9,10). Yet the underlying quantum motion has not so far been observable in real time. Here we study high-harmonic generation in a bulk solid directly in the time domain, and reveal a new kind of strong-field excitation in the crystal. Unlike established atomic sources(1-3,9,11), our solid emits high-harmonic radiation as a sequence of subcycle bursts that coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features are characteristic of a non-perturbative quantum interference process that involves electrons from multiple valence bands. These results identify key mechanisms for future solid-state attosecond sources and next-generation light-wave electronics. The new quantum interference process justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates.