Electronic properties of single-layer antimony: Tight-binding model, spin-orbit coupling, and the strength of effective Coulomb interactions

Tuning the spin-orbit coupling (SOC) in graphene is highly desired for its application in spintronics. In this paper, we calculated the band gap induced by SOC in graphene under uniaxial strain from a tight-binding model, and found that the band gap has a monotonic increasing dependence on the strain in the range of -20% to 15%. Our results suggest that strain can be used as a reversible and controllable way to tune the SOC in graphene. First-principles calculations were performed, confirming the results of tight-binding approximation.

Download Full-text

Quantum anomalous Hall effect on a square lattice with spin–orbit couplings and an exchange field

Canadian Journal of Physics ◽

10.1139/cjp-2013-0241 ◽

2014 ◽

Vol 92 (5) ◽

pp. 420-424 ◽

Cited By ~ 9

Author(s):

Xiaoyong Guo ◽

Xiaobin Ren ◽

Guangjie Guo ◽

Jie Peng

Keyword(s):

Tight Binding ◽

Chern Number ◽

Orbit Coupling ◽

Square Lattice ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Exchange Field ◽

Edge States ◽

Binding Model ◽

Spatial Direction

We investigate a tight-binding model on a two-dimensional square lattice with three terms: the Rashba spin–orbit coupling, the real amplitude next-nearest spin–orbit coupling, and an exchange field. We calculate the first Chern number to identify band topology. It is found that the Chern number takes the quantized values of C1 = 1, 2 and the chiral edge modes can be obtained. Therefore our model realizes the quantum anomalous Hall (QAH) effect. The Rashba coupling is positive for the QAH phase while the next-nearest coupling is detrimental to it. By increasing the exchange field intensity, the Chern number changes from quantized value 2 to 0. The behavior of the edge states is also studied. Particularly for C1 = 2 case, there are two gapless spin-polarized edge states with the same spin polarization moving in the same spatial direction. This indicates that their appearance is topological rather than accidental.

Download Full-text

Electronic Properties of Bulk and Single-Layer MoS2 Using ab Initio DFT: Application of Spin-Orbit Coupling (SOC) Parameters

East European Journal of Physics ◽

10.26565/2312-4334-2020-4-09 ◽

2020 ◽

Keyword(s):

Electronic Properties ◽

Density Functional ◽

Transition Metal Dichalcogenides ◽

Single Layer ◽

Valence Band Maximum ◽

Orbit Coupling ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Monolayer Mos2 ◽

Bulk Mos2

Two dimensional (2D) materials are currently gaining a lot of interest due to excellent properties that are different from their bulk structures. Single and few-layered of Transition metal dichalcogenides (TMDCs) have a bandgap that ranges between 1-2 eV, which is used for FET devices or any optoelectronic devices. Within TMDCs, a ton of consideration is focused on Molybdenum Disulfide (MoS2) because of its promising band gap-tuning and transition between direct to indirect bandgap properties relies upon its thickness. The density functional theory (DFT) calculations with different functionals and spin-orbit coupling (SOC) parameters were carried out to study the electronic properties of bulk and monolayer MoS2. The addition of SOC brought about a noteworthy change in the profile of the band energy, explicitly the splitting of the valence band maximum (VBM) into two sub-bands. The indirect bandgap in bulk MoS2 ranges from 1.17- 1.71eV and that of the monolayer bandgap was 1.6 – 1.71eV. The calculated parameters were compared to the obtained experimental and theoretical results. The obtained density of states (DOS) can be used in explaining the nature of bandgap in both the bulk and monolayer MoS2. These electronic characteristics are important for applications in material devices and energy-saving applications

Download Full-text

Topological viewpoint of two-dimensional group III-V and IV-IV compounds in the presence of electric field and spin-orbit coupling by density functional theory and tight-binding model

Journal of Physics Condensed Matter ◽

10.1088/1361-648x/ac4b7e ◽

2022 ◽

Author(s):

Alireza Baradaran ◽

Mehdi Ghaffarian

Keyword(s):

Electric Field ◽

Density Functional ◽

Tight Binding ◽

Orbit Coupling ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Binding Model ◽

Functional Theory ◽

Group Iii ◽

Topological Phase Transition

Abstract Using the tight-binding model and density functional theory, the topological invariant of the two-dimensional (2D) group III-V and IV-IV compounds are studied in the absence and the presence of an external perpendicular electric field and spin-orbit coupling. It will be recognized that a critical value of these parameters changes the topological invariant of 2D graphene-like compounds. The significant effects of an external electric field and spin-orbit coupling are considered to the two-center overlap integrals of the Slater-Koster model involved in band structures, changing band-gap, and tuning the topological phase transition between ordinary and quantum spin Hall regime. These declare the good consistency between two theories: tight-binding and density functional. So, this study reveals topological phase transition in these materials. Our finding paves a way to extend an effective Hamiltonian, and may instantly clear some computation aspects of the study in the field of spintronic based on the first-principles methods.

Download Full-text

Features due to spin-orbit coupling in the optical conductivity of single-layer graphene

Physical Review B ◽

10.1103/physrevb.81.035421 ◽

2010 ◽

Vol 81 (3) ◽

Cited By ~ 23

Author(s):

P. Ingenhoven ◽

J. Z. Bernád ◽

U. Zülicke ◽

R. Egger

Keyword(s):

Optical Conductivity ◽

Single Layer ◽

Orbit Coupling ◽

Single Layer Graphene ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Layer Graphene

Download Full-text

Plasmon modes in N-layer silicene structures

Journal of Physics Condensed Matter ◽

10.1088/1361-648x/ac3c66 ◽

2021 ◽

Author(s):

Men Nguyen Van

Keyword(s):

Electric Field ◽

Random Phase ◽

Single Layer ◽

Plasmon Mode ◽

Orbit Coupling ◽

Collective Excitations ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Number Of Layers ◽

Plasmon Modes

Abstract We investigate the plasmon properties in N-layer silicene systems consisting of N, up to 6, parallel single-layer silicene under the application of an out-of-plane electric field, taking into account the spin-orbit coupling within the random-phase approximation. Numerical calculations demonstrate that N undamped plasmon modes, including one in-phase optical and (N-1) out-of-phase acoustic modes, continue mainly outside the single-particle excitation area of the system. As the number of layers increases, the frequencies of plasmonic collective excitations increase and can become much larger than that in single layer silicene, more significant for high-frequency modes. The optical (acoustic) plasmon mode(s) noticeably (slightly) decreases with the increase in the bandgap and weakly depends on the number of layers. We observe that the phase transition of the system weakly affects the plasmon properties, and as the bandgap caused by the spin-orbit coupling equal that caused by the external electric field, the plasmonic collective excitations and their broadening function in multilayer silicene behave similarly to those in multilayer gapless graphene structures. Our investigations show that plasmon curves in the system move toward that in single layer silicene as the separation increases, and the impacts of this factor can be raised by a large number of layers in the system. Finally, we find that the imbalanced carrier density between silicene layers significantly decreases plasmon frequencies, depending on the number of layers.

Download Full-text