Liu Jia-Qi, Bian Xue-Bin
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Rev Lett. 2021 Nov 19;127(21):213901. doi: 10.1103/PhysRevLett.127.213901.
High-order harmonic generation (HHG) in solids was expected to be efficient due to their high density. However, the strict transition laws in crystals restrict the number of HHG channels. Quasicrystals with fractal band structures could solve this problem and produce multichannel HHG emissions, which has been rarely studied. We simulate the Fibonacci quasicrystal (FQ) HHG for the first time and investigate the electron dynamics on the attosecond timescale. Our results reveal that (i) the acceleration theorem is approximately applicable in FQ, which provides us a valuable tool to analyze the electron trajectories. (ii) Fractal bands lead to more excitation channels, analogous to the forbidden nonvertical electron transitions in crystals. (iii) The broken symmetry results in more frequent backscattering of electrons. (iv) Compared with crystals, multichannel HHG in FQ has a higher yield and wider spectral range. Our results pave the way to understand and control the HHG in quasicrystals and shed light on a potential shorter and stronger attosecond light source based on compact solids.
由于固体具有高密度，人们曾预期其中的高次谐波产生（HHG）会很高效。然而，晶体中严格的跃迁规律限制了HHG通道的数量。具有分形能带结构的准晶体可以解决这个问题并产生多通道HHG发射，而这方面的研究很少。我们首次模拟了斐波那契准晶体（FQ）的HHG，并在阿秒时间尺度上研究了电子动力学。我们的结果表明：（i）加速定理在FQ中近似适用，这为我们分析电子轨迹提供了一个有价值的工具。（ii）分形能带导致更多的激发通道，类似于晶体中被禁止的非垂直电子跃迁。（iii）对称性破缺导致电子更频繁地背散射。（iv）与晶体相比，FQ中的多通道HHG具有更高的产率和更宽的光谱范围。我们的结果为理解和控制准晶体中的HHG铺平了道路，并为基于紧凑固体的潜在更短更强的阿秒光源提供了线索。
