Photoexcitation of electron wave packets in quantum spin Hall edge states: Effects of chiral anomaly from a localized electric pulse
Photoexcitation of electron wave packets in quantum spin Hall edge states: Effects of chiral anomaly from a localized electric pulse
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DOI：
10.1103/physrevb.94.165412
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发表时间：
2016-09
影响因子：
3.7
通讯作者：
F. Dolcini;R. Iotti;A. Montorsi;F. Rossi
中科院分区：
文献类型：
--
作者：
F. Dolcini;R. Iotti;A. Montorsi;F. Rossi
我们表明，当一个空间局域化的电脉冲施加在量子自旋霍尔系统的边缘，电子波包的螺旋状态可以被光激发纯粹的内部分支电跃迁，而不调用体状态或磁塞曼耦合。特别是，只要电脉冲保持施加，光激发密度失去其右和左移动的特性，而在脉冲结束后，它们在相反的方向上传播而不分散，即保持其空间轮廓不变。值得注意的是，我们发现，而光激发波包的动量分布依赖于温度~$T$和化学势$\mu$的初始平衡状态，并显示出非线性行为的振幅上所施加的脉冲，在介观制度的波包的空间轮廓是独立的$T$和$\mu$。相反，它完全依赖于所施加的电脉冲，以线性方式，作为表征无质量狄拉克电子的手征异常的签名。我们还讨论了光激发波包如何与电脉冲参数进行剪裁，包括低频和有限频率
We show that, when a spatially localised electric pulse is applied at the edge of a quantum spin Hall system, electron wavepackets of the helical states can be photoexcited by purely intra-branch electrical transitions, without invoking the bulk states or the magnetic Zeeman coupling. In particular, as long as the electric pulse remains applied, the photoexcited densities lose their character of right- and left-movers, whereas after the ending of the pulse they propagate in opposite directions without dispersion, i.e. maintaining their space profile unaltered. Notably we find that, while the momentum distribution of the photoexcited wave packets depends on the temperature~$T$ and the chemical potential $\mu$ of the initial equilibrium state and displays a non-linear behavior on the amplitude of the applied pulse, in the mesoscopic regime the space profile of the wave packets is independent of $T$ and $\mu$. Instead, it depends purely on the applied electric pulse, in a linear manner, as a signature of the chiral anomaly characterising massless Dirac electrons. We also discuss how the photoexcited wave packets can be tailored with the electric pulse parameters, for both low and finite frequencies