标题： 通过时间分辨和角度分辨光电子能谱研究LaTe3在电荷密度波能隙上的共振和非共振激发下的不同振幅模态动力学 显示英文标题

标题： Distinct amplitude mode dynamics upon resonant and off-resonant excitation across the charge density wave energy gap in LaTe3 investigated by time- and angle-resolved photoemission spectroscopy

摘要： 由超快激光脉冲产生的非平衡态以特定现象为特征，这些现象在静态测量中无法获得。 先前对稀土三碲化物材料的时间和角度分辨光电子能谱（TARPES）研究揭示了激光驱动的电荷密度波序的熔化及其集体振幅模激发。 材料中通过光学泵浦沉积的过量能量的变化有望为控制动态材料响应提供途径。 为此，我们使用光学参量放大器生成可调谐的泵浦光子能量。 在研究LaTe3时，我们将通过电荷密度波能隙共振泵浦的动力学与在TARPES泵浦-探测实验中使用两倍高光子能量泵浦的效果进行比较。 我们明确识别出泵浦光子能量依赖的行为。 在较大的泵浦光子能量下，过量的电子能量通过电子-声子耦合产生晶格加热，并使振幅模频率从3 THz软化到2 THz。 值得注意的是，跨电荷密度波能隙的共振泵浦导致振幅模频率随时间不变。 我们得出结论，跨能隙的共振激发选择性地激发振幅模，而较高泵浦光子能量下沉积的额外电子过量能量通过非相干耗散过程暂时改变晶体性质。 显示英文摘要

摘要： Non-equilibrium states generated by ultrafast laser pulses are characterized by specific phenomena that are not accessible in static measurements. Previous time- and angle-resolved photoemission spectroscopy (TARPES) studies on rare-earth tritelluride materials have revealed the laser-driven melting of the charge density wave order as well as its collective amplitude mode excitation. Variation of the excess energy deposited by optical pumping in the material promises pathways to control the dynamic material response. To this end, we use an optical parametric amplifier to generate a tunable pump photon energy. Studying LaTe3 we compare the dynamics driven by pumping resonantly across the charge density wave energy gap with the effect of pumping at a twice higher photon energy in a TARPES pump-probe experiment. We clearly identify a pump photon energy dependent behavior. At the larger pump photon energy, the excess electronic energy generates lattice heating mediated by e-ph coupling and softening of the amplitude mode frequency from 3 to 2 THz. Remarkably, the resonant pumping across the CDW gap results in a time-independent amplitude mode frequency. We conclude that the resonant excitation across the energy gap excites the amplitude mode selectively while additional electronic excess energy deposited at higher pump photon energy modifies the crystal properties transiently by incoherent dissipative processes.