第一性原理时间分辨光电子能谱学对准粒子光穿和光脱的实时监测
Monitoring in real time the photon-dressing and undressing of quasiparticles from first principles time-resolved photoelectron spectroscopy
摘要：
固体的光泵浦产生非平衡电子结构，其中电子和光子结合形成修饰电子态的准粒子。由此产生的电子能级移动被称为光学斯塔克效应，在光谱中可见为红移。在这里，我们表明，在泵浦探测设置，我们可以唯一地定义一个非平衡准粒子能带结构，可以直接测量与光电子能谱。多体电子态的动态光子修饰（和去修饰）可以通过泵浦-探测时间和角分辨光电子能谱学（tr-ARPES）来监测，因为光子修饰的能带结构随泵浦-探测脉冲重叠的时间演化。计算得到的tr-ARPES谱在最大重叠处与Floquet理论的准能谱完全一致，当泵浦-探测重叠趋于零时，谱趋于平衡态.此外，我们还展示了这种随时间变化的非平衡准粒子结构如何被理解为光学斯塔克效应的能带结构。扩展到自旋分辨PES可以用来预测非对称的二向色性响应与谷选择性的光激发在单层过渡金属二硫属化物（TMD）。
英文摘要：
Optical pumping of solids creates a non-equilibrium electronic structure where electrons and photons combine to form quasiparticles of dressed electronic states. The resulting shift of electronic levels is known as the optical Stark effect, visible as a red shift in the optical spectrum. Here we show that in a pump-probe setup we can uniquely define a non-equilibrium quasiparticle bandstructure that can be directly measurable with photo-electron spectroscopy. The dynamical photon-dressing (and undressing) of the many-body electronic states can be monitored by pump-probe time and angular resolved photoelectron spectroscopy (tr-ARPES) as the photon-dressed bandstructure evolves in time depending on the pump-probe pulse overlap. The computed tr-ARPES spectrum agrees perfectly with the quasi-energy spectrum of Floquet theory at maximum overlap and goes to the the equilibrium bandstructure as the pump-probe overlap goes to zero. Additionally, we show how this time-dependent non-equilibrium quasiparticle structure can be understood to be the bandstructure underlying the optical Stark effect. The extension to spin-resolved PES can be used to predict asymmetric dichroic response linked to the valley selective optical excitations in monolayer transition metal dichalcogenides (TMDs).
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