6533b82afe1ef96bd128b9dd

RESEARCH PRODUCT

Single-Hemisphere Photoelectron Momentum Microscope With Time-of-Flight Recording

D. VasilyevS. BabenkovGerd SchönhenseHans-joachim ElmersKaterina Medjanik

subject

Spectrum analyzerMicroscopePhysics - Instrumentation and DetectorsFOS: Physical sciencesAngle-resolved photoemission spectroscopyApplied Physics (physics.app-ph)01 natural sciences010305 fluids & plasmaslaw.inventionMomentumOpticslaw0103 physical sciencesInstrumentation010302 applied physicsPhysicsCondensed Matter - Materials Sciencebusiness.industryResolution (electron density)Materials Science (cond-mat.mtrl-sci)Physics - Applied PhysicsInstrumentation and Detectors (physics.ins-det)Brillouin zoneTime of flightbusinessExcitation

description

Photoelectron momentum microscopy is an emerging powerful method for angle-resolved photoelectron spectroscopy (ARPES), especially in combination with imaging spin filters. These instruments record kx-ky images, typically exceeding a full Brillouin zone. As energy filters double-hemispherical or time-of-flight (ToF) devices are in use. Here we present a new approach for momentum mapping of the full half-space, based on a single hemispherical analyzer (path radius 225 mm). Excitation by an unfocused He lamp yielded an energy resolution of 7.7 meV. The performance is demonstrated by k-imaging of quantum-well states in Au and Xe multilayers. The alpha-square-aberration term (alpha: entrance angle in the dispersive plane) and the transit-time spread of the electrons in the spherical field are studied in a large pass-energy (6 to 660 eV) and angular range (alpha up to about 7{\deg}). It is discussed how the method circumvents the preconditions of previous theoretical work on the resolution limitation due to the alpha-square-term and the transit-time spread, being detrimental for time-resolved experiments. Thanks to k-resolved detection, both effects can be corrected numerically. We introduce a dispersive-plus-ToF hybrid mode of operation, with an imaging ToF analyzer behind the exit slit of the hemisphere. This instrument captures 3D data arrays I(EB,kx,ky), yielding a gain up to N^2 in recording efficiency (N being the number of resolved time slices). A key application will be ARPES at sources with high pulse rates like Synchrotrons with 500 MHz time structure.

https://dx.doi.org/10.48550/arxiv.2007.16095