Gotta Catch ‘Em All: Detecting the full photoemission cone from laser-based ARPES experiments by leveraging deflector technology

Angle-resolved photoemission spectroscopy (ARPES) provides a direct access to the electronic band structure of materials. The momentum range accessible by this technique depends directly on the photon energy used, and low photon energies (such as 6 eV sources commonly used in time-resolved ARPES) are insufficient to photoemit electrons over the full Brillouin zone of most quantum materials. In addition, while electrons are emitted over a 2π solid angle, conventional hemispherical analyzers only collect a partial slice (typically +/- 15 deg along one direction). A previous work [RSI 92, 123907 (2021)] demonstrated that a complete slice (+/- 180 degrees) can be acquired in one fixed configuration by accelerating electrons towards the analyzer with a bias voltage. However, the model presented is only applicable when the sample surface is normal to the analyzer axis and the complete 2π solid angle can only be obtained by azimuthal sample rotation. Here, we extend this work by leveraging the deflector technology of novel ARPES analyzers. We demonstrate the ability to detect all 2π photoemitted electrons in a fixed configuration for various materials such as gold and cuprate superconductors. This approach is especially advantageous for time-resolved ARPES [RMP 96, 015003 (2024)], as electron dynamics over a large momentum range can be accessed with identical measurement conditions.