Anomalous intense coherent secondary photoemission from a perovskite oxide

Journal article

Photocathodes—materials that convert photons into electrons through a phenomenon known as the photoelectric effect—are important for many modern technologies that rely on light detection or electron-beam generation^1,2,3. However, current photocathodes are based on conventional metals and semiconductors that were mostly discovered six decades ago with sound theoretical underpinnings^4,5. Progress in this field has been limited to refinements in photocathode performance based on sophisticated materials engineering^1,6. Here we report unusual photoemission properties of the reconstructed surface of single crystals of the perovskite oxide SrTiO₃(100), which were prepared by simple vacuum annealing. These properties are different from the existing theoretical descriptions^4,7,8,9,10. In contrast to other photocathodes with a positive electron affinity, our SrTiO₃ surface produces, at room temperature, discrete secondary photoemission spectra, which are characteristic of efficient photocathode materials with a negative electron affinity^11,12. At low temperatures, the photoemission peak intensity is enhanced substantially and the electron beam obtained from non-threshold excitations shows longitudinal and transverse coherence that differs from previous results by at least an order of magnitude^6,13,14. The observed emergence of coherence in secondary photoemission points to the development of a previously undescribed underlying process in addition to those of the current theoretical photoemission framework. SrTiO₃ is an example of a fundamentally new class of photocathode quantum materials that could be used for applications that require intense coherent electron beams, without the need for monochromatic excitations.

Authors: Hong, C; Zou, W; Ran, P; Tanaka, K; Matzelle, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer Nature
• Journal: Nature
• Volume: 617
• Issue: 7961
• Pages: 493-498
• Publication date: 2023-03-08
• Acceptance date: 2023-02-28
• DOI: 10.1038/s41586-023-05900-4
• EISSN: 1476-4687
• ISSN: 0028-0836
• Language: English