Measurement station for ultrafast terahertz-driven photoemission spectroscopy

超快太赫兹驱动光电子能谱测量站

• 批准号: 465668329
• 金额: --
• 依托单位: Universität Bielefeld
• 依托单位国家: 德国
• 项目类别: Major Research Instrumentation
• 财政年份: 2022
• 资助国家: 德国
• 起止时间: 2021-12-31 至 无数据
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465668329?language=en
• 关键词: Measurement; station; ultrafast; terahertz; driven

The proposed instrument essentially combines tailored strong-field terahertz (THz) excitation with time-resolved angular-resolved photoemission spectroscopy (tr-ARPES) experiment. It will allow us to observe, with sub-cycle time resolution and fast enough to prevent the surface degradation, the ultrafast nonequilibrium dynamics in a wide class of materials, under unique conditions of powerful “bottom-up” excitation of each material’s fundamental, lowest-energy modes with THz radiation. Physical problems such as energy flow and the development of ultrafast non-equilibrium in Dirac materials (e.g. graphene, 3D Dirac semimetals, topological insulators), magnetic materials (e.g. rare-earth orthoferrites), Peierls semimetals (bismuth or arsenic) and van der Waals heterostructures (e.g. WSe2) will be studied, under the unique conditions of direct excitation of lowest-energy modes in the materials (conduction currents around the Fermi level, infrared-active optical phonons, magnons). “Bottom-up” THz excitation of materials will avoid the parasitic excitations of electronic or lattice subsystems, such as in the case of ultrafast optical excitation, leading to electronic band-to-band transitions and Raman excitation of the lattice. Using ARPES, we will thus be able to directly observe the effect of bottom-up energy deposition into the material on bandstructure and population. Further, the effect of photoemission itself in the presence of external strong THz-fields will be studied, by photoelectron streaking in “slower” (multi-)THz driving fields, as compared to typically used infrared signals. This will provide us unique access to longer timescales in photoemission dynamics. Our setup will be powered by a femtosecond laser delivering the pulses of 5 mJ energy and central wavelength of 1030 nm, at a repetition rate of 100 kHz. The laser will be equipped with light conversion stages allowing emission from EUV to THz. The high repetition rate of the laser enables the acquisition of time- and angle-resolved photoemission data in short enough acquisition times to prevent sample surface degradation. This will allow us to perform our experiments on a wide class of “vulnerable” materials, such as (semi-)metals, semiconductors, magnetic materials, molecular-decorated surfaces etc. As an electron analyzer, the momentum microscope will be used, which, apart from the information on the energy-momentum dependency of the photoemitting electronic state, also allows operation in an imaging mode for sample inspection. A variable temperature sample stage will allow us, in particular, to study the dynamics of materials undergoing phase transitions. The relatively high pulse energy of the driving laser of 5 mJ will enable strong-field THz generation via optimized optical rectification, yielding single- and multi-cycle THz pulses with electric field strength in the rage 0.1 – 1 MV/cm, and with the frequency content 0.1 – 40 THz.

所提出的仪器本质上将定制的强场太赫兹（THz）激发与时间分辨角分辨光电子能谱（tr-ARPES）实验结合起来，它将使我们能够以子周期时间分辨率和足够快的速度进行观察，以防止表面发生。在太赫兹辐射对每种材料的基本、最低能量模式进行强大的“自下而上”激发的独特条件下，各种材料中的超快非平衡动力学物理问题。例如狄拉克材料（例如石墨烯、3D狄拉克半金属、拓扑绝缘体）、磁性材料（例如稀土正铁氧体）、佩尔斯半金属（铋或砷）和范德华异质结构中的能量流和超快非平衡的发展（例如 WSe2) 将在材料中最低能量模式的直接激发的独特条件下进行研究（费米能级周围的传导电流、红外活性光学声子、磁振子）材料的“自下而上”太赫兹激发将避免电子或晶格子系统的寄生激发，例如在超快光学激发的情况下，从而导致电子。使用 ARPES，我们将能够直接观察自下而上的能量沉积到材料中的效果。此外，与通常使用的红外信号相比，将通过“较慢”（多）太赫兹驱动场中的光电子条纹来研究光电子发射本身在外部强太赫兹场中的影响。我们在光电子发射动力学中获得了更长时间尺度的独特途径，我们的装置将由飞秒激光器提供动力，以 1030 nm 的重复率提供 5 mJ 能量的脉冲。 100 kHz 激光器将配备光转换级，允许从 EUV 发射到太赫兹，从而能够在足够短的采集时间内采集时间和角度分辨的光发射数据，以防止样品表面退化。将使我们能够对多种“脆弱”材料进行实验，例如（半）金属、半导体、磁性材料、分子装饰表面等。作为电子分析仪，将使用动量显微镜，它，除了有关光发射电子态的能量动量依赖性的信息之外，还允许在成像模式下进行样品检查，特别是，可变温度样品台将允许我们研究经历相变的材料的动力学。 5 mJ的驱动激光器的高脉冲能量将通过优化的光学整流实现强场太赫兹产生，产生电场强度在0.1 – 1 MV/cm范围内的单周期和多周期太赫兹脉冲，频率为内容 0.1 – 40 太赫兹。