Palladium diselenide (${\mathrm{PdSe}}_2$), 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, has not yet been explored. By applying polarization-dependent, angle-resolved photoemission spectroscopy and density functional theory calculations, we measured an indirect band gap of bulk ${\mathrm{PdSe}}_2$ to be $\sim 0.36\mathrm{eV}$. Moreover, the orbital-resolved electronic band structure reveals a top valence band dominated by Pd-$d_{3z^2-r^2}$ and Se-$p_z$ 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 ${\mathrm{PdSe}}_2$ and propose ${\mathrm{PdSe}}_2$ to be an intrinsically orbital-engineered material with giant anisotropy for polarization-related optical applications.

Close

PrevNext

View figure in article

• Band gap
• Density functional theory
• Electronic structure
• Layered semiconductors
• Polarization
• Angle-resolved photoemission spectroscopy