论文标题
在二维动量空间中观察到的拓扑表面状态下的超快电子动力学
Ultrafast electron dynamics in a topological surface state observed in two-dimensional momentum space
论文作者
论文摘要
我们在SB $ _2 $ _2 $ _3 $ _3 $的二维动量空间中研究超快人口动态，并具有时间和角度分辨的两光子光发射。线性偏光泵脉冲用于允许跨狄拉克点的直接光激发。我们表明，这种共振激发在狄拉克锥体中沿六个$ \barγ$ - $ \ bar {m} $方向中的三个中的三个方向强烈增强，并在沿$ \barγ$ - $ \ bar {k} $方向对齐时产生宏观的光电流。我们的实验方法使能够以前所未有的细节在整个Dirac锥体内部弹性和非弹性电子散射来消除瞬时激发群体的衰减和光电腐蚀性。这是用来表明SB $ _2 $ _2 $ _3 $ _3 $的掺杂强烈增强了无弹性电子散射至降低能量，但仅影响迪拉克锥体周围的弹性散射。
We study ultrafast population dynamics in the topological surface state of Sb$_2$Te$_3$ in two-dimensional momentum space with time- and angle-resolved two-photon photoemission. Linear polarized mid-infrared pump pulses are used to permit a direct optical excitation across the Dirac point. We show that this resonant excitation is strongly enhanced within the Dirac cone along three of the six $\barΓ$-$\bar{M}$ directions and results in a macroscopic photocurrent when the plane of incidence is aligned along a $\barΓ$-$\bar{K}$ direction. Our experimental approach makes it possible to disentangle the decay of transiently excited population and photocurent by elastic and inelastic electron scattering within the full Dirac cone in unprecedented detail. This is utilized to show that doping of Sb$_2$Te$_3$ by vanadium atoms strongly enhances inelastic electron scattering to lower energies, but only scarcely affects elastic scattering around the Dirac cone.
