Time-resolved ARPES with tunable 12–21.6 eV XUV at 400 kHz repetition rate

Time-resolved and angle-resolved photoemission spectroscopy (trARPES) is a powerful method to detect the non-equilibrium electronic structure in solid systems. In this study, we report a trARPES apparatus with tunable photon energy selectively among 12, 16.8, and 21.6 eV at a repetition rate of 400 kHz. The energy and temporal resolutions of the three harmonics are determined as 104/111/157 meV and 276/190/154 fs, respectively. The photon flux on the sample is estimated to be 1010–1011 photons/s by using a photodiode. Finally, the performance of this setup is verified by both equilibrium and non-equilibrium ARPES measurements on topological materials Zr2Te2P and Bi2Se3. Meanwhile, the importance of the tunability of the extreme ultraviolet (XUV) source is highlighted by comparing experimental results measured with the three different photon energies.