Title：Unusual materials properties of Cu-containing semiconductors：The role of metal d orbitals

Speaker：Su-Huai Wei  Beijing Computational Science Research Center

Time：Aug 15, 2022 10：30am

Venue：333，Physics Building

Online report（ Tencent ID:600 781 753）

Abstract：It has been shown that most semiconductors exhibit a metal d subband near or inside the main valence band. Using band structure calculation techniques, which treat the outermost d electrons on the same footing as other valence electrons, we study their effects on the material properties. We find that p-d and/or s-d repulsion and hybridization (i) lower the band gaps, (ii) reduce the deformation potential of the valence band maximum states, (iii) increase the band offsets between common anion compounds, (iv) reduce the spin-orbit splitting, (v) alter the sign of the crystal-field splitting, and (vi) is responsible for the negative exchange splitting in magnetic semiconductors. Among all the metal elements, Cu has the highest fully occupied d orbital energy which is close to its unoccupied s orbital, thus cuprates, Cu chalcogenides, and Cu halides often exhibit some unusual physical properties such as unusual crystal structures and band structures, deep Cu acceptor levels in II-VI semiconductors, fast ionic diffusion, ultralow thermal conductivity, and even superconductivity. In this talk, I will discuss the electronic origin for these unusual behaviors.