发表机构
Louisiana State University; Binghamton University（路易斯安那州立大学; 宾汉姆顿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过半导体布洛赫方程模拟，利用阿秒瞬态吸收将MoS₂的Mo 4p半芯边作为谷偏振测量仪，实现了载流子分辨的谷偏振测量，可实时追踪谷偏振的产生与演化。
AI 中文摘要
近年来，二维半导体中谷偏振的全光写入与开关已在飞秒时间尺度得到验证，但在相同时间尺度下逐个载流子读取该偏振仍未实现。通过对单层MoS₂进行半导体布洛赫方程模拟，我们证明阿秒瞬态吸收可填补这一空白，将Mo 4p半芯边转变为定量谷偏振测量仪。我们发现，泵浦诱导的芯价吸收探测空穴，而芯导带漂白探测电子，因此单张光谱可通过光吸收能量区分每种载流子。空穴通道在平衡态下受泡利阻塞，以无背景形式出现，其圆二色性随泵浦螺旋度反转符号，归一化幅度与谷偏振成正比。最后，我们证明扫描探针延迟可实时记录数飞秒的写入过程，因此阿秒芯能级二色性是一种对载流子敏感的定量探针，可用于谷偏振的产生与演化研究。
英文摘要
In recent years, all-optical writing and switching of valley polarization in two-dimensional semiconductors has been demonstrated on femtosecond timescales. Reading this polarization out on the same timescale, carrier by carrier, has so far remained out of reach. Employing semiconductor Bloch equation simulations of monolayer MoS$_2$, we show that attosecond transient absorption closes this gap by turning the Mo $4p$ semicore edge into a quantitative valley polarimeter. We find that pump-enabled core-to-valence absorption probes the holes while core-to-conduction bleaching probes the electrons, so that a single spectrum identifies each carrier by its photoabsorption energy. The hole channel, Pauli-blocked in equilibrium, emerges background-free. Its circular dichroism reverses sign with the pump helicity, and its normalized magnitude is proportional to the valley polarization. Finally, we show that scanning the probe delay clocks the few-femtosecond write in real time. Thus, attosecond core-level dichroism is a carrier-sensitive, quantitative probe of the creation and evolution of valley polarization.
Comments20 pages, 4 figures, 3 tables. Supplemental Material will be available with the journal publication
