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

Fumihiko Matsui; Kenta Hagiwara; Eiken Nakamura; Takayuki Yano; Hiroyuki Matsuda; Yasuaki Okano; Satoshi Kera; Eri Hashimoto; Shinji Koh; Keiji Ueno; Takahiro Kobayashi; Emi Iwamoto; Kazuyuki Sakamoto; Shin-Ichiro Tanaka; Shigemasa Suga

doi:10.1063/5.0154156

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

Rev Sci Instrum. 2023 Aug 1;94(8):083701. doi: 10.1063/5.0154156.

Authors

Fumihiko Matsui^{1

2}, Kenta Hagiwara¹, Eiken Nakamura¹, Takayuki Yano¹, Hiroyuki Matsuda¹, Yasuaki Okano¹, Satoshi Kera^{1

2}, Eri Hashimoto³, Shinji Koh³, Keiji Ueno⁴, Takahiro Kobayashi⁵, Emi Iwamoto⁵, Kazuyuki Sakamoto^{5

6}, Shin-Ichiro Tanaka⁷, Shigemasa Suga^{7

8}

Affiliations

¹ UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan.
² The Graduate University for Advanced Studies, SOKENDAI, Okazaki, Aichi 444-8585, Japan.
³ College of Science and Engineering, Aoyama Gakuin University, Sagamihara 252-5258, Japan.
⁴ Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan.
⁵ Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
⁶ Spintronics Research Network Division, OTRI, Osaka University, Suita, Osaka 565-0871, Japan.
⁷ SANKEN, Osaka University, Ibaraki, Osaka 567-0047, Japan.
⁸ PGI-6, Jülich Research Center, Jülich, Germany.

PMID: 38065145
DOI: 10.1063/5.0154156

Abstract

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 μm-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 Å-1 or real space with a radius of a few 100 μm 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 (hν), 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 μm-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.