Spin-orbit splitting and piezoelectric properties of Janus GeXY (X ≠ Y = P, As, Sb and Bi)

• Published in: Physical chemistry chemical physics : PCCP Vol. 25; no. 24; pp. 16559 - 16569
• Main Authors: Liu, Hui-Ying, Wang, Yue-Yi, Chen, Ze-Yan, Hou, Ting-Ping, Wu, Kai-Ming, Lin, Heng-Fu
• Format: Journal Article
• Published: 21.06.2023
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d2cp05805g

The coexistence of spin-orbit coupling and piezoelectricity in a single material may have potential application in multifunctional devices, including spintronics, nanorobotics and piezotronics. Spin-orbit coupling provides a new means to manipulate electron's spin without an additional external magnetic field, while piezoelectricity refers to the interplay between mechanical stresses and electric polarization. Using first-principles calculations, the structural, electronic, optical, spin, and piezoelectric properties of the Janus Ge 2 XY (X ≠ Y = P, As, Sb, and Bi) monolayers were systematically investigated. All the Ge 2 XY are energetically and dynamically stable in the α phase. At the GW level, Ge 2 AsSb, Ge 2 AsBi, and Ge 2 SbBi have direct fundamental band gaps of 0.65, 0.64, and 0.91 eV. At the GW + BSE level, their optical gaps are 0.42, 0.45, and 0.63 eV, and the optical absorption coefficients can reach about 10 −5 cm −1 in the infrared light region, which reveals that they have potential for application in infrared photodetectors. For Ge 2 PBi, Ge 2 AsBi, and Ge 2 SbBi containing the heavy Bi element, the lowermost conduction band and uppermost valence band have large spin splitting along the M - K and K - Γ lines, and the bands near the Fermi level possess Rashba spin splitting at the Γ point. Ge 2 PBi and Ge 2 SbBi have both large in-plane piezoelectric coefficients d 11 (−0.75 and −3.18 pm V −1 ) and out-of-plane piezoelectric coefficients d 31 (0.37 and 0.30 pm V −1 ). Our findings are helpful to understand the mechanism of the spin-orbit physics and piezoelectricity of Janus Ge 2 XY monolayers and guide experiments in exploring novel multifunctional materials. The structural, electronic, spin-orbit splitting and piezoelectric properties of monolayer Janus α-Ga 2 XY (X ≠ Y = P, As, Sb, and Bi) were systematically investigated.