Structural, electronic and optical properties of bulk and monolayer iron diselenide: A density functional study

Abstract Using the density functional theory (DFT), we study the electronic structure and linear optical properties of pyrite and monolayer structure of FeSe 2 . Calculated results show that pyrite FeSe 2 is a non-magnetic semiconductor material, while hexagonal monolayer FeSe 2 show completely metallic features. There have strong hybridizations between Fe- d orbitals and Se- p orbitals. All optical properties such as real and imaginary parts of dielectric function, absorption coefficient, reflectivity and loss function are obtained and analyzed. The results present obvious anisotropy in optical features of monolayer FeSe 2 and excellent absorption properties in ultraviolet and visible light regions. Results show that the anti-ferromagnetic character in pyrite FeSe 2 turn into ferromagnetic character for hexagonal monolayer and the main transitions near the Fermi level mainly contributed by down-spin carriers. From the density of states, we found thet the Fe- d orbitals play an important role in the interband and intraband transitions. These results made monolayer FeSe 2 an ideal candidate for photovoltaic, opto-electric and spintronic applications.