First-principles modeling of 3d-transition-metal-atom adsorption on silicene: a linear-response DFT + U approach

Achieving controllable multifunctionality through layer sliding

Dynamical variation of physical properties in a controllable fashion provides exciting possibilities to obtain multifunctional materials. In this work, layer-sliding is employed to modify the structural, interfacial electronic and optical properties of unintercalated and Mg-intercalated two-dimensional (2D) van der Waals heterostructure (vdW-HS) consisting of buckled silicene and hexagonal boron nitride (hBN). The most stable stacking configuration of silicene over hBN is screened out and then intercalated with Mg at the interface. Dynamical-dependent changes in the properties of vdW-HS are performed by sliding silicene over hBN monolayer in the absence and presence of the intercalant. Layer-sliding is carried out in equal length intervals, and various parametric quantities related to the physical characteristics of the vdW-HS are repeatedly calculated and compared. Apart from various parametric quantities, stability of unintercalated and Mg-intercalated vdW-HS is also checked by means of relative total energies, binding energies and vdW gaps along the sliding pathway. Comparison of binding energies shows that the un-slided, half-slided, and fully-slided Mg-intercalated vdW-HS are 1.52, 1.44 and 1.42 eV more stable than the unintercalated vdW-HS. Opening of a small band gap of 12, 31 and 28 meV for un-slided, half-slided and fully-slided unintercalated vdW-HS, respectively, is worth mentioning. To study the interfacial electronic behavior, planar average charge density difference (Δρ) and charge transfer (ΔQ) are also calculated and varied via layer-sliding. Further, we calculated diverse optical spectra such as the complex dielectric function (DF), electron energy loss function [L(ω)], diagonal components of dielectric tensor [ε(iω)], refractive index [n(ω)], extinction coefficient [k(ω)], absorption coefficient [α(ω)], and reflectivity [R(ω)] for un-slided, half-slided and fully-slided unintercalated and Mg-intercalated vdW-HS. Interestingly, the polarization and energy losses have been reduced in the case of Mg-intercalated vdW-HS. The suggested layer-sliding method can be established as a general scheme for bringing multifunctionality into a layered material.

Strain Controlled Ferromagnetic-Antiferromagnetic Transformation in Mn-Doped Silicene for Information Transformation Devices

A reliable control of magnetic states is central to the use of magnetic nanostructures. Here, by using state-of-the-art density-functional theory calculations, we find that Mn atoms decorated silicene has an anomalously fixed magnetic moment and a high Curie temperature. In addition, a tunable magnetic exchange coupling is achieved for Mn-silicene system with the application of biaxial strain, which induces a transformation from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. As such, an atomic "bit" could be obtained by superimposing strain field once the FM and AFM states are referred to as "1" and "0". Such piezospin nanodevices, which convert mechanical energy into magnetic moment, would offer great potential for future information transmission, as they ultimately combine small size, high-speed operation, and low-power consumption.