학술논문
Time- and momentum-resolved photoemission studies using time-of-flight momentum microscopy at a free-electron laser
Document Type
Working Paper
Author
Kutnyakhov, Dmytro; Xian, Rui Patrick; Dendzik, Maciej; Heber, Michael; Pressacco, Federico; Agustsson, Steinn Ymir; Wenthaus, Lukas; Meyer, Holger; Gieschen, Sven; Mercurio, Giuseppe; Benz, Adrian; Bühlman, Kevin; Däster, Simon; Gort, Rafael; Curcio, Davide; Volckaert, Klara; Bianchi, Marco; Sanders, Charlotte; Miwa, Jill Atsuko; Ulstrup, Søren; Oelsner, Andreas; Tusche, Christian; Chen, Ying-Jiun; Vasilyev, Dmitrii; Medjanik, Katerina; Brenner, Günter; Dziarzhytski, Siarhei; Redlin, Harald; Manschwetus, Bastian; Dong, Shuo; Hauer, Jasper; Rettig, Laurenz; Diekmann, Florian; Rossnagel, Kai; Demsar, Jure; Elmers, Hans-Joachim; Hofmann, Philip; Ernstorfer, Ralph; Schönhense, Gerd; Acremann, Yves; Wurth, Wilfried
Source
Review of Scientific Instruments 91, 013109 (2020)
Subject
Language
Abstract
Time-resolved photoemission with ultrafast pump and probe pulses is an emerging technique with wide application potential. Real-time recording of non-equilibrium electronic processes, transient states in chemical reactions or the interplay of electronic and structural dynamics offers fascinating opportunities for future research. Combining valence-band and core-level spectroscopy with photoelectron diffraction for electronic, chemical and structural analysis requires few 10 fs soft X-ray pulses with some 10 meV spectral resolution, which are currently available at high repetition rate free-electron lasers. The PG2 beamline at FLASH (DESY, Hamburg) provides a high pulse rate of 5000 pulses/s, 60 fs pulse duration and 40 meV bandwidth in an energy range of 25-830 eV with a photon beam size down to 50 microns in diameter. We have constructed and optimized a versatile setup commissioned at FLASH/PG2 that combines FEL capabilities together with a multidimensional recording scheme for photoemission studies. We use a full-field imaging momentum microscope with time-of-flight energy recording as the detector for mapping of 3D band structures in ($k_x$, $k_y$, $E$) parameter space with unprecedented efficiency. Our instrument can image full surface Brillouin zones with up to 7 {\AA} $^{-1}$ diameter in a binding-energy range of several eV, resolving about $2.5\times10^5$ data voxels. As an example, we present results for the ultrafast excited state dynamics in the model van der Waals semiconductor WSe$_2$.