Browsing by Subject "Spin polarization"
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Item Open Access Compressibility of a two-dimensional electron gas in a parallel magnetic field(Elsevier B.V., 2007) Subaşi, A. L.; Tanatar, BilalThe thermodynamic compressibility of a two-dimensional electron system in the presence of an in-plane magnetic field is calculated. We use accurate correlation energy results from quantum Monte Carlo simulations to construct the ground state energy and obtain the critical magnetic field Bc required to fully spin polarize the system. Inverse compressibility as a function of density shows a kink-like behavior in the presence of an applied magnetic field, which can be identified as Bc. Our calculations suggest an alternative approach to transport measurements of determining full spin polarization.Item Open Access Electronic structure of conventional slater type antiferromagnetic insulators: AIrO3 (A=Sr, Ba) perovskites(Institute of Physics, 2022) Koc, Husnu; Mamedov, Amirullah M.; Özbay, EkmelThe structural, mechanical, and electronic properties of Perovskite BaIrO3 and SrIrO3 compounds based on the density functional theory (DFT) have been examined in four different structures (C2/c, R-3m, P6_3/mmc and Pm-3m) and Pnma structure, respectively. The spin polarized generalized gradient approximation has been used for modeling exchange-correlation effects. As a result of spin polarized calculations, it has been observed that BaIrO3 compound showed magnetic properties in C2/c and R-3m structures, but not in Pm-3m and P6_3/mmc structures. SrIrO3 compound also shows magnetic properties in Pnma structure. The elastic constants have been calculated using the strain-stress method and the other related quantities (the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, sound velocities, and Debye temperature) have also been estimated. In electronic band structure calculations, while Pm-3m and P6_3/mmc structures of NaIrO3 compound are metallic and semiconductor (Eg = 1.190 eV indirect), respectively, while C2/c and R-3m structures showing magnetic properties are metallic in spin down state and semiconductor (Eg=0.992 eV indirect and Eg=0.665 eV direct, respectively) in the spin up state. The Pmna structure in the SrIrO3 compound is a semiconductor in both spin states (Eg=0.701 eV “0.632 eV” indirect in the spin up “spin down”). © 2022 Institute of Physics Publishing. All rights reserved.Item Open Access Half-metallic silicon nanowires: First-principles calculations(American Physical Society, 2007) Durgun, Engin; Çakır, D.; Akman, N.; Çıracı, SalimFrom first-principles calculations, we predict that specific transition metal (TM) atom-adsorbed silicon nanowires have a half-metallic ground state. They are insulators for one spin direction, but show metallic properties for the opposite spin direction. At high coverage of TM atoms, ferromagnetic silicon nanowires become metallic for both spin directions with high magnetic moment and may have also significant spin polarization at the Fermi level. The spin-dependent electronic properties can be engineered by changing the type of adsorbed TM atoms, as well as the diameter of the nanowire. Present results are not only of scientific interest, but also can initiate new research on spintronic applications of silicon nanowires. © 2007 The American Physical Society.Item Open Access Magnetic ground state in FeTe2,VS2, and NiTe2 monolayers: antiparallel magnetic moments at chalcogen atoms(American Physical Society, 2020) Aras, M.; Kılıç, Ç.; Çıracı, SalimOur analysis based on the results of hybrid and semilocal density-functional calculations with and without Hubbard U correction for on-site Coulomb interactions reveals the true magnetic ground states of three transition-metal dichalcogenide monolayers, viz., FeTe2,VS2, and NiTe2, which comprise inhomogeneous magnetic moment configurations. In contrast to earlier studies considering only the magnetic moments of transition-metal atoms, the chalcogen atoms by themselves have significant, antiparallel magnetic moments owing to the spin polarization through p−d hybridization. The latter is found to be true for both H and T phases of FeTe2,VS2, and NiTe2 monolayers. Our predictions show that the FeTe2 monolayer in its lowest-energy structure is a half metal, which prevails under both compressive and tensile strains. Half metallicity occurs also in the FeTe2 bilayer but disappears in thicker multilayers. The VS2 monolayer is a magnetic semiconductor; it has two different band gaps of different character and widths for different spin polarization. The NiTe2 monolayer, which used to be known as a nonmagnetic metal, is indeed a magnetic metal with a small magnetic moment. These monolayers with intriguing electronic and magnetic properties can attain new functionalities for spintronic applications.Item Open Access Magnetization and spin susceptibility of an interacting two-dimensional electron gas(American Institute of Physics, 2007) Subaşı, Ahmet Levent; Tanatar, BilalWe study the magnetic behavior and in particular the spin susceptibility of an interacting two-dimensional electron gas in a finite in-plane magnetic field. The total energy of the system is constructed using the recent quantum Monte Carlo simulation based parametrized correlation energy as a function of density, spin polarization, and applied magnetic field. The critical magnetic field to fully spin polarize the system is obtained as a function of the electron density. The spin polarization as a function of the applied field (less than the critical field) for various densities are calculated. The spin susceptibility as a function of the applied field for various densities are calculated. The zero-field value of the spin susceptibility as a function of electron density is compared with relevant experiments.Item Open Access Tuning electronic properties of monolayer hexagonal boron phosphide with group III-IV-V dopants(American Chemical Society, 2017-02) Onat, B.; Hallioglu, L.; Ipek, S.; Durgun, EnginAn extensive study on doping of two-dimensional (2D) hexagonal boron phosphide (h-BP) which is a direct band gap semiconductor was performed by using ab initio methods based on spin-polarized density functional theory. The interaction of group III-IV-V elements with h-BP is explored, considering both adsorption and substitution cases, and the resulting structural and electronic properties are examined. The variation of adsorption (substitution) energies and band gap values are systematically analyzed and trends are identified. Upon adsorption, the most of the elements bound on top of P atom forming dumbbell geometry which generates characteristic spin-polarized impurity states. The substitution of B or P by group III-IV-V elements can produce extra electrons/holes which lead to n-type and p-type doping for adequate cases. Additionally, doping can further generate impurity resonant states. Functionalization of h-BP with adatoms can tune the electronic structure and would be useful for nanoelectronic applications in low-dimensions.