So far, it has been assumed that selective excitation of a desired valley in the Brillouin zone of a hexagonal two-dimensional material has to rely on using circularly polarized fields. We theoretically demonstrate a way to control the valley excitation in hexagonal 2D materials on a few-femtosecond timescale using a few-cycle, linearly polarized pulse with controlled carrier–envelope phase. The valley polarization is mapped onto the strength of the perpendicular harmonic signal of a weak, linearly polarized pulse, which allows to read this information all-optically without destroying the valley state and without relying on the Berry curvature, making our approach potentially applicable to inversion-symmetric materials. We show applicability of this method to hexagonal boron nitride and ${{\rm MoS}_2}$.

中文翻译：

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子周期Valleytronics：使用几个周期的线性极化脉冲控制谷底极化

到目前为止，已经假定六方二维材料的布里渊区的期望谷的选择性激发必须依赖于使用圆偏振场。我们从理论上证明了一种方法，该方法使用几个周期的线性极化脉冲，在受控的载波-包络相位下，在几飞秒的时间尺度上控制六角形2D材料中的波谷激发。谷底极化被映射到一个弱，线性极化脉冲的垂直谐波信号的强度上，这使得可以在不破坏谷底状态且不依赖贝里曲率的情况下全光读取该信息，这使得我们的方法可能适用于反演不对称材料。我们展示了该方法对六方氮化硼和$ {{\ rm MoS} _2} $的适用性。