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量身定制的强场terahertz（THZ）与时间分辨的角度分辨光发射光谱（TR-ARPES）实验结合在一起。它将使我们能够通过亚周期时间分辨率观察，并且足够快以防止表面降解，在宽类材料中的超快非平衡动力学，在每种材料基本的，最低的能量模式的强大“自下而上”的兴奋下，具有THZ辐射。诸如狄拉克材料（例如石墨烯，3D狄拉克半仪，拓扑绝缘子），磁性材料（例如，稀有的近距离铁岩），peierls semimetals（bismituth或arsenic）和范德华（Van der waals）的条件（例如，范围内的excrution offort offort offort offort offort offort offort of Under）的物理问题，例如能量流量和超快非平衡的发展材料中最低的能量模式（材料的传统电流“自下而上”将避免对电子或晶格子系统的寄生兴奋，例如在超快的光学兴奋的情况下，导致电子带对伴随的过渡和材料的兴奋，从而使材料的兴奋能够直接效应。与典型使用的红外信号相比，在存在外部强的THZ场上，光发射本身的效果将被研究。我们的设置将由飞秒激光器提供动力，以5 MJ能量和1030 nm的中心波长的脉冲，重复速率为100 kHz。激光将等效于光转换阶段，从而使EUV发射到THZ。激光的高重复速率使得在足够短的采集时间内获得时间和角度分辨的光发射数据，以防止样品表面降解。这将使我们能够对广泛的“脆弱”材料进行实验，例如（半）金属，半导体，磁性材料，分子表面等作为电子分析仪，将使用动量显微镜，除了有关电子依赖的电子状态的信息外，还允许进行电子效应的信息，还允许进行电子效应的信息。可变的温度样品阶段将使我们特别可以研究相变的材料动力学。 5 MJ的驱动激光器的相对高脉冲能将通过优化的光学整流来实现强场THZ的产生，从而在rage 0.1 - 1 mV/cm的频率中产生具有电场强度的单周和多循环THZ脉冲，并且频率含量为0.1 - 40 THz。