Soft x-ray photoelectron momentum microscope for multimodal valence band stereography

The photoelectron momentum microscope (PMM) in operation at BL6U, an undulator-based soft x-ray beamline at the UVSOR Synchrotron Facility, offers a new approach for mu m-scale momentum-resolved photoelectron spectroscopy (MRPES). A key feature of the PMM is that it can very effectively reduce radiation-induced damage by directly projecting a single photoelectron constant energy contour in reciprocal space with a radius of a few angstrom(-1) or real space with a radius of a few 100 mu m onto a two-dimensional detector. This approach was applied to three-dimensional valence band structure E(k) and E(r) measurements (stereography) as functions of photon energy (hv), its polarization (e), detection position (r), and temperature (T). In this study, we described some examples of possible measurement techniques using a soft x-ray PMM. We successfully applied this stereography technique to mu m-scale MRPES to selectively visualize the single-domain band structure of twinned face-centered-cubic Ir thin films grown on Al2O3(0001) substrates. The photon energy dependence of the photoelectron intensity on the Au(111) surface state was measured in detail within the bulk Fermi surface. By changing the temperature of 1T-TaS2, we clarified the variations in the valence band dispersion associated with chiral charge-density-wave phase transitions. Finally, PMMs for valence band stereography with various electron analyzers were compared, and the advantages of each were discussed.

Automated summary

The photoelectron momentum microscope (PMM) is a new method that can effectively reduce radiation-induced damage by projecting a single photoelectron energy contour onto a two-dimensional detector. It has been used for measuring the three-dimensional valence band structure and energy variations in different experimental conditions. This technique has been successfully applied to observe the band structure of thin films and investigate the changes in photoelectron energy and band structure in different materials. Furthermore, comparisons and discussions of different PMMs with various electron analyzers have been conducted.