Valley polarization control in WSe2 monolayer by a single-cycle laser pulse
Valley polarization control in WSe2 monolayer by a single-cycle laser pulse
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DOI：
10.1103/physrevb.105.115403
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发表时间：
2022-03
影响因子：
3.7
通讯作者：
Arqum Hashmi;Shunsuke Yamada;A. Yamada;K. Yabana;T. Otobe
中科院分区：
文献类型：
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作者：
Arqum Hashmi;Shunsuke Yamada;A. Yamada;K. Yabana;T. Otobe
二维材料中的山谷自由度为扩展电子山谷装置的功能提供了机会。极短的谷区寿命要求对谷区伪自旋进行超快控制。在这里，我们从理论上论证了用单周期线偏振激光脉冲控制单层中的谷假自旋。我们利用载流子包络相位(CEP)控制的非对称电场使布里渊区(BZ)中点与点之间的谷极化。自旋-轨道相互作用的含时密度泛函理论表明，在线性光学极限范围内，没有观察到谷非对称性及其对CEP的依赖关系。在非线性光学区域，线偏振脉冲引起高度的谷极化，并且这种偏振对于场强是很强健的。谷极化强烈依赖于CEP，并作为CEP的函数振荡。随着激光强度的增加，载流子密度分布呈节点状分布，我们的结果表明，载流子密度在BZ中的位置可以由激光强度控制。根据质量狄拉克哈密顿模型的分析，载流子密度的节点可以归结为电子波函数的波包的朗道-齐纳-斯特克尔伯格干涉。
The valley degree of freedom in two-dimensional materials provides an opportunity to extend the functionalities of valleytronic devices. Very short valley lifetimes demand the ultrafast control of valley pseudospin. Here we theoretically demonstrate the control of valley pseudospin inmonolayer by a single-cycle linearly polarized laser pulse. We use the asymmetric electric field controlled by the carrier-envelope phase (CEP) to make the valley polarization betweenandpoint in the Brillouin zone (BZ). Time-dependent density functional theory with spin-orbit interaction reveals that no valley asymmetry and its CEP dependence is observed within the linear-optical limit. In the nonlinear-optical regime, a linearly polarized pulse induces a high degree of valley polarization and this polarization is robust against the field strength. Valley polarization strongly depends and oscillates as a function of CEP. The carrier density distribution forms nodes as the laser intensity increases, our results indicate that the position of the carrier density in the BZ can be controlled by the laser intensity. From the analysis by the massive Dirac Hamiltonian model, the nodes of the carrier density can be attributed to the Landau-Zener-Stückelberg interference of wave packets of the electron wave function.