arXiv subjects

B. H. Mehdiyev

Publications and source records attributed to B. H. Mehdiyev.

7 recordsLinked to original sources

arXiv2017

A new topological insulator - β-InTe strained in the layer plane

We have investigated the band structure of the bulk crystal and the (001) surface of the β-InTe layered crystal subjected to biaxial stretching in the layer plane. The calculation has been carried out using the full-potential linearized augmented plane wave method (FP LAPW) implemented in WIEN2k. It has been shown that at the strain \Deltaa/a=0.06, where a is the lattice parameter in the layer plane, the band gap in the electronic spectrum collapses. With further strain increase a band inversion occurs. The inclusion of the spin-orbit interaction reopens the gap in the electronic spectrum of a bulk crystal, and our calculations show that the spectrum of the surface states has the form of a Dirac cone, typical for topological insulators.

cond-mat.mtrl-sci↗

arXiv2017

Prediction of half-metallic properties in TlCrS2 and TlCrSe2 based on density functional theory

Half-metallic properties of TlCrS2, TlCrSe2 and hypothetical TlCrSSe have been investigated by first-principles all-electron full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method based on density functional theory (DFT). The results of calculations show that TlCrS2 and TlCrSSe are half-metals with energy gap (Eg ) ~0.12 ev for spin-down channel. Strong hybridization of p-state of chalchogen and d-state of Cr leads to bonding and antibonding states and subsequently to the appearance of a gap in spin-down channel of TlCrS2 and TlCrSSe. In the case of TlCrSe2, there is a partial hybridization and p-state is partially present in the DOS at Fermi level making this compound nearly half- metallic. The present calculations revealed that total magnetic moment keeps its integer value on a relatively wide range of changes in volume (-10% 10%) for TlCrS2 and TlCrSSe, while total magnetic moment of TlCrSe2 decreases with increasing volume approaching to integer value 3μB.

cond-mat.mtrl-sci↗

arXiv2016

First principles calculation of the valence band offsets for \b{eta}- polytype of A3B6 layered crystals

The valence band offsets (VBO) for the \b{eta}-type A3B6 layered compounds depending on the thickness of the crystals have been investigated from the first principles, based on the density functional theory. To simulate the structure of a given thickness the periodic slab model was used. Two adjacent crystal slabs consisting of several layers were separated by a vacuum region of two-layer width. It is shown that at the crystal thickness more than 12 layers, photothreshold practically becomes independent on the thickness of the crystal.

cond-mat.mtrl-sci↗

arXiv2014

Surface phonons in two-layer thin films of GeSe

This paper presents ab inition calculations of the surface phonon spectra of GeSe layered semiconductor compound, based on the Density Functional Perturbation Theory (DFPT). The surface has been imitated by a structure of periodically arranged slabs of two layers of GeSe crystal separated from other identical layers by the layers of vacuum sufficiently wide to ignore the effect of the upper boundary of the double-layer upon its lower boundary. We discuss the character of the surface modes located in the gaps, in the pockets, and in the area of allowed phonon states for the bulk GeSe crystals, as well as outside (above and below) the boundaries of the bulk phonon states.

cond-mat.mtrl-sci↗

arXiv2014

Second-order phase transition at high-pressure in A4B6 crystals

The existence of second-order structural phase transition in the SnS at a pressure of 16 GPa has been proved theoretically. The calculation is performed using the plane-wave pseudopotential approach to density-functional theory within the local-density approximation (LDA) with the help of the ABINIT software package. The abrupt change in volume compression with unit cell volume continuous change of the crystal is the clear evidence of the second-order phase transition. It is shown that the phase transition is caused by the softening of the low-frequency fully symmetric interlayer mode with increasing pressure. As a result, displacement type phase transition (PT) take place with the change of translational symmetry of the crystal from the simple orthorhombic to the base-centered orthorhombic (Pcmn to Cmcm).

cond-mat.mtrl-sci↗

arXiv2013

The pressure dependence of the phonon spectra and elastic modulus of orthorhombic : the method of local density functional

The IR- and Raman-active phonon frequencies, as well as the elastic constants of orthorhombic GeSe, were calculatedas a function of hydrostatic pressure using the method of density functional in the ABINIT software package. Comparison with the published results of theoretical calculations and experimental data of the pressure dependence of Raman-active phonons has been carried out. Our calculations show that at a pressure of about 29 GPa the crystal structure of GeSe undergoes a continuous transition from simple orthorhombic to base-centered orthorhombic lattice.

cond-mat.mtrl-sci↗

arXiv2004

Interband electron Raman scattering in a quantum wire in a transverse magnetic field

Electron Raman scattering (ERS) is investigated in a parabolic semiconductor quantum wire in a transverse magnetic field neglecting by phonon-assisted transitions. The ERS cross-section is calculated as a function of a frequency shift and magnetic field. The process involves an interband electronic transition and an intraband transition between quantized subbands. We analyze the differential cross-section for different scattering configurations. We study selection rules for the processes. Some singularities in the Raman spectra are found and interpreted. The scattering spectrum shows density-of-states peaks and interband matrix elements maximums and a strong resonance when scattered frequency equals to the "hybrid" frequency or confinement frequency depending on the light polarization. Numerical results are presented for a GaAs/AlGaAs quantum wire.

cond-mat.mes-hall↗