Matrix Element Effect in Layered PdSe2

Palladium diselenide (PdSe₂), a novel two-dimensional dichalcogenide, has garnered widespread attention due to its exceptional optoelectronic properties. Unveiling the matrix element effect in layered semiconducting materials is essential for optimizing the performance of optoelectronic devices. However, no dedicated study has yet been reported on the photon energy and temperature dependence of this effect in PdSe₂. In this work, we conducted a direct investigation of the electronic band structure of PdSe₂ as a function of temperature, employing photon-energy-dependent angle-resolved photoemission spectroscopy (ARPES). The wave vector asymmetry and signal drop at the valence band maximum stem from the matrix elements involved in the photoemission process. This effect is influenced by both the sample’s temperature and the photon energy. Our findings provide clear, direct evidence of the matrix element effect in PdSe₂, which is dependent on both the temperature and photon energy.