Palladium diselenide (PdSe2), a recently exploited transition metal dichalcogenide material with a thickness-dependent band gap, anisotropic optical response, and high air stability, has shown excellent performance in electronics and polarization photodetection. However, the origin of the intriguing optical response in this material from a perspective of electronic band structure, including the orbital character and the experimental demonstration of its indirect band gap, hasn’t yet been explored.
By applying polarization-dependent angle-resolved photoemission spectroscopy and density functional theory calculations, we measured an indirect band gap of bulk PdSe2 to be ~ 0.36 eV. Moreover, the orbital-resolved electronic band structure reveals a top valence band dominated by Pd-3d and Se-2p orbitals, which gives rise to an unprecedented giant linear dichroic ratio of ~ 10, showing a huge orbital-induced anisotropy.
Our results elucidate the semiconducting nature of PdSe2 and propose PdSe2 to be an intrinsically orbital-engineered material with giant anisotropy for polarization-related optical applications. This work has been published recently on Physical Review B:
Phys. Rev. B 106, L121110 (2021)
DOI: 10.1103/PhysRevB.106.L121110
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.L121110
PhD candidate Chenyi Gu from the research group is the first author of the paper. Prof. Yuefeng Nie and Prof. Feng Miao are the corresponding authors. Prof. Jian Zhou from Nanjing University provided assistance on the DFT calculations. Prof. Eli Rotenberg from LBNL and Prof. Yulin Chen from Oxford University provided assistance on the synchrotron based ARPES.
