The Experts below are selected from a list of 22353 Experts worldwide ranked by ideXlab platform
O N Mryasov - One of the best experts on this subject based on the ideXlab platform.
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Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in a co 0001 h bn co 0001 magnetic tunnel junction
Physical Review B, 2015Co-Authors: Sergey V Faleev, Stuart S P Parkin, O N MryasovAbstract:The 'Brillouin Zone spin filtering' mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJ) and studied on an example of the MTJ with hcp Co electrodes and hexagonal BN (h-BN) spacer. Our calculations based on local density approximation of density functional theory (LDA-DFT) for Co(0001)/h-BN/Co(0001) MTJ predict high TMR in this device due to Brillouin Zone filtering mechanism. Owning to the specific complex band structure of the h-BN the spin-dependent tunneling conductance of the system is ultra-sensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport propertied of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and p-doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory (STT-MRAM).
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Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in a co 0001 h bn co 0001 magnetic tunnel junction
Physical Review B, 2015Co-Authors: Sergey V Faleev, Stuart S P Parkin, O N MryasovAbstract:The Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJs) and studied for an example of the MTJ with hcp Co electrodes and hexagonal BN $(h$-BN) spacer. Our calculations based on the local density approximation of density-functional theory (LDA-DFT) for $\text{Co}(0001)/h\text{-BN}/\text{Co}(0001)$ MTJ predict high TMR in this device due to Brillouin Zone filtering mechanism. Owning to the specific complex band structure of the $h$-BN the spin-dependent tunneling conductance of the system is ultrasensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport properties of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and $p$-doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory.
Caio H Lewenkopf - One of the best experts on this subject based on the ideXlab platform.
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tight binding model for the band dispersion in rhombohedral topological insulators over the whole Brillouin Zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulators materials with the space group $D^{5}_{3d}(R\bar{3}m)$. The model describes the bulk band structure of these materials over the whole Brillouin Zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac cone-like dispersion and the emergence of surface projected bulk states near to the Dirac-point in energy. We find that the breaking of the $R_{3}$ symmetry as one moves away from the $\Gamma$ point has an important role in the hybridization of the $p_x$, $p_y$, and $p_z$ atomic orbitals. In our tight-binding model, the latter leads to a band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
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tight binding model for the band dispersion in rhombohedral topological insulators over the whole Brillouin Zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulator materials with the space group ${D}_{3d}^{5}(R\overline{3}m)$. The model describes the bulk band structure of these materials over the whole Brillouin Zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac conelike dispersion and the emergence of surface projected bulk states near to the Dirac point in energy. We find that the breaking of the ${R}_{3}$ symmetry as one moves away from the $\mathrm{\ensuremath{\Gamma}}$ point has an important role in the hybridization of the ${p}_{x}, {p}_{y}$, and ${p}_{z}$ atomic orbitals. In our tight-binding model, the latter leads to a band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
Sergey V Faleev - One of the best experts on this subject based on the ideXlab platform.
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Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in a co 0001 h bn co 0001 magnetic tunnel junction
Physical Review B, 2015Co-Authors: Sergey V Faleev, Stuart S P Parkin, O N MryasovAbstract:The 'Brillouin Zone spin filtering' mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJ) and studied on an example of the MTJ with hcp Co electrodes and hexagonal BN (h-BN) spacer. Our calculations based on local density approximation of density functional theory (LDA-DFT) for Co(0001)/h-BN/Co(0001) MTJ predict high TMR in this device due to Brillouin Zone filtering mechanism. Owning to the specific complex band structure of the h-BN the spin-dependent tunneling conductance of the system is ultra-sensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport propertied of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and p-doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory (STT-MRAM).
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Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in a co 0001 h bn co 0001 magnetic tunnel junction
Physical Review B, 2015Co-Authors: Sergey V Faleev, Stuart S P Parkin, O N MryasovAbstract:The Brillouin Zone spin filtering mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJs) and studied for an example of the MTJ with hcp Co electrodes and hexagonal BN $(h$-BN) spacer. Our calculations based on the local density approximation of density-functional theory (LDA-DFT) for $\text{Co}(0001)/h\text{-BN}/\text{Co}(0001)$ MTJ predict high TMR in this device due to Brillouin Zone filtering mechanism. Owning to the specific complex band structure of the $h$-BN the spin-dependent tunneling conductance of the system is ultrasensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport properties of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and $p$-doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory.
Carlos Mera Acosta - One of the best experts on this subject based on the ideXlab platform.
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tight binding model for the band dispersion in rhombohedral topological insulators over the whole Brillouin Zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulators materials with the space group $D^{5}_{3d}(R\bar{3}m)$. The model describes the bulk band structure of these materials over the whole Brillouin Zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac cone-like dispersion and the emergence of surface projected bulk states near to the Dirac-point in energy. We find that the breaking of the $R_{3}$ symmetry as one moves away from the $\Gamma$ point has an important role in the hybridization of the $p_x$, $p_y$, and $p_z$ atomic orbitals. In our tight-binding model, the latter leads to a band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
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tight binding model for the band dispersion in rhombohedral topological insulators over the whole Brillouin Zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulator materials with the space group ${D}_{3d}^{5}(R\overline{3}m)$. The model describes the bulk band structure of these materials over the whole Brillouin Zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac conelike dispersion and the emergence of surface projected bulk states near to the Dirac point in energy. We find that the breaking of the ${R}_{3}$ symmetry as one moves away from the $\mathrm{\ensuremath{\Gamma}}$ point has an important role in the hybridization of the ${p}_{x}, {p}_{y}$, and ${p}_{z}$ atomic orbitals. In our tight-binding model, the latter leads to a band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
Emilian Nica - One of the best experts on this subject based on the ideXlab platform.
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glide reflection symmetry Brillouin Zone folding and superconducting pairing for the p 4 n m m space group
Physical Review B, 2015Co-Authors: Emilian NicaAbstract:Motivated by the studies of the superconducting pairing states in the iron-based superconductors, we analyze the effects of Brillouin Zone folding procedure from a space-group symmetry perspective for a general class of materials with the $P4/nmm$ space group. The Brillouin Zone folding amounts to working with an effective 1-Fe unit cell, instead of the crystallographic 2-Fe unit cell. We show that the folding procedure can be justified by the validity of a glide reflection symmetry throughout the crystallographic Brillouin Zone and by the existence of a minimal double degeneracy along the edges of the latter. We also demonstrate how the folding procedure fails when a local spin-orbit coupling is included although the latter does not break any of the space-group symmetries of the bare Hamiltonian. In light of these general symmetry considerations, we further discuss the implications of the glide reflection symmetry for the superconducting pairing in an effective multiorbital $t\ensuremath{-}{J}_{1}\ensuremath{-}{J}_{2}$ model. We find that, for spin-singlet pairing states, the P4/$nmm$ space-group symmetry allows only even parity under the glide reflection and zero total momentum.