Creation and control of valley currents in graphene by few cycle light pulses: Data storage

Journal Ref: npj Comput Mater 11, 185 (2025). DOI: https://doi.org/10.1038/s41524-025-01689-0 Well established for the visible spectrum gaps of the transition metal dichalcogenide family, valleytronics—the control of valley charge and current by light—is comparatively unexplored for the THz gaps that characterize graphene and topological insulators. Here we show that few cycle pulses of THz light can create and control a >90% valley polarized current in graphene, with lightwave control over the current magnitude and direction. This is underpinned by a light-matter symmetry breaking in the ultrafast limit of circularly polarized light, characterized by a symmetry lowering of the excited state charge distribution. Our findings both highlight the richness of few cycle light pulses in control over quantum matter, and provide a route towards a “THz valleytronics” in meV gapped systems.期刊引用：《npj计算材料学》11卷，第185页（2025年）。 DOI：https://doi.org/10.1038/s41524-025-01689-0 针对过渡金属硫族化合物（transition metal dichalcogenide, TMD）家族的可见光带隙体系，谷电子学（valleytronics）——即通过光调控谷电荷与谷电流——的研究已较为成熟；但对于石墨烯与拓扑绝缘体所表征的太赫兹（terahertz, THz）带隙体系，谷电子学的相关研究仍相对匮乏。本文证明，太赫兹少周期光脉冲可在石墨烯中产生并调控谷极化度超过90%的谷电流，且可通过光波直接控制电流的幅值与方向。这一现象的核心机制是圆偏振光超快极限下的光-物质对称性破缺，其特征为激发态电荷分布的对称性降低。本研究成果既彰显了少周期光脉冲在量子物质调控领域的丰富应用潜力，也为能隙处于毫电子伏特（millielectronvolt, meV）尺度的体系实现"THz谷电子学"提供了可行路径。