arXiv subjects

Meijuan Cheng

Publications and source records attributed to Meijuan Cheng.

3 recordsLinked to original sources

arXiv2021

Strong bulk photovoltaic effect and second-harmonic generation in two-dimensional selenium and tellurium

Few-layer selenium and tellurium films have been recently prepared, and they provide a new platform to explore novel properties of two-dimensional (2D) elemental materials. In this work, we have performed a systematic first-principles study on the electronic, linear, and nonlinear optical (NLO) properties of atomically thin selenium and tellurium films within the density-functional theory with the generalized gradient approximation plus scissors correction using the band gaps from the relativistic hybrid Heyd-Scuseria-Ernzerhof functional calculations. Interestingly, we find that few-layer Se and Te possess large second-harmonic generation (SHG), linear electro-optic effect, and bulk photovoltaic effect. In particular, trilayer (TL) Te possesses large SHG coefficient, being more than 65 times larger than that of GaN, a widely used NLO material. Bilayer (BL) Te has huge static SHG coefficient, being more than 100 times larger than that of GaN. Furthermore, monolayer (ML) Se possesses large SHG coefficient. Moreover, we predict that TL Te exhibits strong bulk photovoltaic effect (BPVE), being greater than that of GeS, a polar system with the largest BPVE found so far. Although the shift current conductivities of bulk and 2D Se are comparable, the shift current conductivities of TL Te are five times larger than those of bulk Te. Finally, an analysis of the calculated electronic band structures indicates that the strong NLO responses of 2D Se and Te materials are primarily derived from their low-dimensional structures with high anisotropy, directional covalent bonding, lone-pair electrons, and relatively small band gaps. These findings provide a practical strategy to search for excellent NLO and BPVE materials.

physics.optics↗

arXiv2020

Significant Second-Harmonic Generation and Bulk Photovoltaic Effect in Trigonal Selenium and Tellurium Chains

One-dimensional selenium and tellurium crystalize in helical chainlike structures and thus exhibit fascinating properties. By performing first-principles calculations, we have researched the linear and nonlinear optical (NLO) properties of 1D Se and Te, and find that both systems exhibit pronounced NLO responses. In particular, 1D Se is found to possess large second-harmonic generation coefficient being up to 7 times larger than that of GaN, and even is several times larger than that of the bulk counterpart. On the other hand, 1D Te also produces significant NLO susceptibility which exceeds the bulk GaN by 5 times. Furthermore, 1D Te is shown to possess prominent linear electro-optic coefficient rxxx(0). Particularly, Te chain exhibits large shift current response and the maximum is more than the maximal photovoltaic responses obtained from BaTiO3 by 2 times. Therefore, 1D Se and Te may find potential applications in solar energy conversion, electro-optical switches, and so on. Finally, much stronger NLO effects of 1D Se and Te are attributed to their one-dimensional structures with high anisotropy, strong covalent bonding and lone-pair electrons. These findings will contribute to the further study in experiments and search for excellent materials with large NLO effects.

physics.optics↗

arXiv2019

Large Second-Harmonic Generation and Linear Electro-Optic Effect in Trigonal Selenium and Tellurium

Trigonal selenium and tellurium crystalize in helical chain-like structures and thus possess interesting properties such as current-induced spin polarization, gyrotropic effects and nonlinear optical responses. By performing systematic ab initio calculations based on density functional theory in the generalized gradient approximation plus scissors correction, we study their linear and nonlinear optical (NLO) properties. We find that the two materials exhibit significant second-harmonic generation (SHG) and linear electro-optic (LEO) effect. In particular, the SHG coefficients of tellurium are huge in the photon energy range of 0 ~ 3 eV, with the magnitudes of SHG(xxx) being as large as 3640 pm/V, which are about sixteen times larger than that of GaN, a widely used NLO material. On the other hand, trigonal selenium is found to possesses large LEO coefficients r(xxx,0) which are more than six times larger than that of GaN.Therefore, trigonal tellurium and selenium may find valuable applications in NLO and LEO devices such as frequency conversion, electro-optical switch and light signal modulator.The energy positions and shapes of the principal features in the calculated optical dielectric functions of both materials agree rather well with the available experimental ones, and are also analyzed in terms of the calculated band structures especially symmetries of the involved band states and dipole transition selection rules.

physics.comp-ph↗