Linear AC transport in T-stub and crossed silicene nanosystems

2018 ◽  
Vol 32 (03) ◽  
pp. 1850016
Author(s):  
Yun-Lei Sun ◽  
En-Jia Ye
Keyword(s):  
Electric Field ◽  
Transport Properties ◽  
External Electric Field ◽  
Nearest Neighbor ◽  
Transport Theory ◽  
Energy Gap ◽  
Local Density ◽  
Tight Binding ◽  
Edge State ◽  
Topological Quantum

In this work, we theoretically study the linear AC transport properties in T-stub and crossed zigzag silicene nanosystems. The DC conductance and AC emittance are numerically calculated based on the tight-binding approach and AC transport theory, by considering the nearest-neighbor hopping, second-nearest-neighbor spin-orbit interaction (SOI) and external electric field. The relatively strong SOI of silicene was demonstrated to induce a topological quantum edge state in the nanosystems by the local density of states, which eliminates the AC emittance response at the Dirac point. Further investigations suggest that the SOI-induced AC transport is topologically protected from the changes of geometrical size. Moreover, the AC transport properties of these nanosystems can be tuned by the external electric field, which would open an energy gap and destroy the topological quantum state, making them trivial band insulators.

ENERGY GAP DEPENDENCE ON ANION CONCENTRATION FOR GaxIn1-xAsyP1-y QUATERNARY ALLOY BY RECURSION METHOD

2004 ◽  
Vol 18 (18) ◽  
pp. 955-962
Author(s):  
MUSA EL-HASAN ◽  
REZEK ESTATIEH
Keyword(s):  
Density Of States ◽  
Energy Gap ◽  
Local Density ◽  
Tight Binding ◽  
Quaternary Alloy ◽  
Average Density ◽  
Local Density Of States ◽  
Recursion Method ◽  
Orbital Decomposition ◽  
Lattice Matched

Three terminators have been tested, square root terminator, quadreture terminator and linear terminator, it was found that the linear terminator is the best, so it was used in calculating local density of states (LDOS) and it's orbital decomposition, alloy average density of states, and energy gap for different anion concentrations for InP lattice matched alloy. The results were compared with our previous calculations of (LDOS), and results from other methods. Energy gap was compared with experimental measurements. A five orbital sp3s* per atom model was used in the tight-binding representation of the Hamiltonian.

Near-surface transport properties of donor doped Pb(ZrxTi1−x)O3 (PZT) in an external electric field

2012 ◽  
Vol 225 ◽  
pp. 727-731 ◽  
Author(s):  
T. Frömling ◽  
H. Hutter ◽  
C. Leach ◽  
N.K. Ali ◽  
K. Reichmann ◽  
...  
Keyword(s):  
Electric Field ◽  
Transport Properties ◽  
External Electric Field ◽  
Near Surface ◽  
Surface Transport

scholarly journals Density Functional Theory Study of CL-20/Nitroimidazoles Energetic Cocrystal Compounds in an External Electric Field

2021 ◽  
Author(s):  
xiaosong Xu ◽  
Renfa Zhang ◽  
Wenxin Xia ◽  
Peng Ma ◽  
Congming Ma ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
Nitro Group ◽  
External Electric Field ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Functional Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Abstract The external electric field has a significant influence on the sensitivity of the energetic cocrystal materials. In order to find out the relationship between the external electric field and sensitivity of energetic cocrystal compounds 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-2,4-dinitro-1H-imidazole (CL-20/2,4-MDNI) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-4,5-dinitro-1H-imidazole (CL-20/4,5-MDNI). In this work, density functional theory (DFT) at B3LYP-D3/6-311+G(d,p) and M062X-D3/ma-def2 TZVPP levels was employed to calculate the bond dissociation energies (BDEs) of selected N-NO2 trigger bonds, frontier molecular orbitals, electrostatic potentials (ESPs) and nitro group charges (QNO2) under different external electric field. The results show that as the positive electric field intensity increases, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy gap and BDEs become smaller, and the local positive ESPs becomes larger, so that the energetic cocrystals tends to have higher sensitivity. In addition, the linear fitting results show that the trigger bond length and nitro group charge changes are closely related to the external electric field strength.

Degradation of bromobenzene via external electric field

2020 ◽  
Vol 19 (01) ◽  
pp. 2050004 ◽  
Author(s):  
Yu Chen ◽  
Yuzhu Liu ◽  
Qihang Zhang ◽  
Yihui Yan ◽  
Wenyi Yin
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Energy Charge ◽  
Level Energy ◽  
Homo Level ◽  
Lumo Level ◽  
Dissociation Barrier

Bromobenzene is one of the organic pollutants that damage the natural environment and poses a serious threat to human health. Therefore, it is meaningful to study its degradation characteristics under the electric field. In this paper, density functional theory (DFT) at BPV86/6-311G (d, p) level are employed for the study of C–Br bond distance, total energy, charge distribution, dipole moment, lowest unoccupied molecular orbital (LUMO) level, highest occupied molecular orbital (HOMO) level, energy gap and potential energy surface (PES) of bromobenzene in external electric field ([Formula: see text]15.43[Formula: see text]V[Formula: see text][Formula: see text][Formula: see text]nm[Formula: see text]–15.43[Formula: see text]V[Formula: see text][Formula: see text][Formula: see text]nm[Formula: see text]). It shows that as the electric field increases, the C–Br bond tends to break. The changes in the HOMO level and the LUMO level result in a rapid drop in the energy gap. In addition, the dissociation barrier gradually decreases. When the applied electric field reaches 15.43[Formula: see text]V[Formula: see text][Formula: see text]nm[Formula: see text], the dissociation barrier disappears completely, which means that the C–Br bond is broken and bromobenzene is degraded.

scholarly journals Design of boron vacancy enhanced spin filtering graphene/BN zigzag nanoribbon heterojunctions

RSC Advances ◽  
2017 ◽  
Vol 7 (12) ◽  
pp. 7368-7374 ◽  
Author(s):  
Xiaohui Jiang ◽  
Dongqing Zou ◽  
Bin Cui ◽  
Changfeng Fang ◽  
Wen Liu ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Electric Field ◽  
Transport Properties ◽  
External Electric Field ◽  
Electronic Transport ◽  
Graphene Nanoribbons ◽  
Electronic Transport Properties ◽  
Spin Polarized ◽  
Boron Nitride Nanoribbons ◽  
Zigzag Graphene Nanoribbons

The spin-polarized electronic transport properties of zigzag graphene nanoribbons (ZGNRs) and boron nitride nanoribbons (ZBNNRs) heterojunctions with a boron vacancy are investigated under an external electric field.

scholarly journals Electrically and magnetically switchable nonlinear photocurrent in РТ-symmetric magnetic topological quantum materials

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Hua Wang ◽  
Xiaofeng Qian
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Time Reversal ◽  
Magnetic Transition ◽  
Microscopic Theory ◽  
Zeeman Splitting ◽  
Magnetic Structures ◽  
Topological Quantum ◽  
Frequency Regime ◽  
Quantum Materials

AbstractNonlinear photocurrent in time-reversal invariant noncentrosymmetric systems such as ferroelectric semimetals sparked tremendous interest of utilizing nonlinear optics to characterize condensed matter with exotic phases. Here we provide a microscopic theory of two types of second-order nonlinear direct photocurrents, magnetic shift photocurrent (MSC) and magnetic injection photocurrent (MIC), as the counterparts of normal shift current (NSC) and normal injection current (NIC) in time-reversal symmetry and inversion symmetry broken systems. We show that MSC is mainly governed by shift vector and interband Berry curvature, and MIC is dominated by absorption strength and asymmetry of the group velocity difference at time-reversed ±k points. Taking $${\cal{P}}{\cal{T}}$$ P T -symmetric magnetic topological quantum material bilayer antiferromagnetic (AFM) MnBi2Te4 as an example, we predict the presence of large MIC in the terahertz (THz) frequency regime which can be switched between two AFM states with time-reversed spin orderings upon magnetic transition. In addition, external electric field breaks $${\cal{P}}{\cal{T}}$$ P T symmetry and enables large NSC response in bilayer AFM MnBi2Te4, which can be switched by external electric field. Remarkably, both MIC and NSC are highly tunable under varying electric field due to the field-induced large Rashba and Zeeman splitting, resulting in large nonlinear photocurrent response down to a few THz regime, suggesting bilayer AFM-z MnBi2Te4 as a tunable platform with rich THz and magneto-optoelectronic applications. Our results reveal that nonlinear photocurrent responses governed by NSC, NIC, MSC, and MIC provide a powerful tool for deciphering magnetic structures and interactions which could be particularly fruitful for probing and understanding magnetic topological quantum materials.

Effect of the Local Disorder in a-Si on the Electronic Density of States at the Band Edges.

1991 ◽  
Vol 219 ◽  
Author(s):  
B. N. Davidson ◽  
G. Lucovsky ◽  
J. Bernholc
Keyword(s):  
Density Of States ◽  
Nearest Neighbor ◽  
Bond Angle ◽  
Local Density ◽  
Tight Binding ◽  
Bethe Lattice ◽  
Neighbor Interaction ◽  
Lattice Method ◽  
Electronic Density ◽  
Interaction Terms

ABSTRACTWe have systematically investigated the formation of electronic states in the region of the conduction and valence band edges of a Si as functions of variations in the bond angle distributions. Local Density of States (LDOS) for Si atoms in disordered environments have been calculated using the cluster Bethe lattice method with a tight-binding Hamiltonian containing both first and second nearest neighbor interaction terms. LDOS for atoms with bond angle dis ortions in the nearest neighbor and second neighbor shells are compared and contrasted, both showing an influence on the LDOS near the gap. We also consider the role of the second neighbor term in the Hamiltonian by comparing the DOS for a distoned infinite Bethe lattice using Hamiltonians with and without the second neighbor interactions. It is found that in this case the second neighbor interaction terms cause greater conduction band tailing than using the nearest neighbor interaction terms alone.

Defect States and Structural Disorder in a-Si.

1992 ◽  
Vol 258 ◽  
Author(s):  
B. N. Davidson ◽  
G. Lucovsky ◽  
J. Bernholc
Keyword(s):  
Standard Deviation ◽  
Nearest Neighbor ◽  
Bond Angle ◽  
Local Density ◽  
Tight Binding ◽  
Bethe Lattice ◽  
Structural Disorder ◽  
Defect States ◽  
Lattice Method ◽  
The Relationship

ABSTRACTWe have examined the distribution of the neutral dangling bond defect states, T30, as a function of the local disorder. T30 defects in a-Si play an important role in many of the current models of the metastable photoconductivity. To understand the relationship between the T30 defect and its bonding environment, the Local Density of States (LDOS) for under-coordinated Si atoms in disordered environments are calculated using the cluster-Bethe lattice method, CBLM. Our Hamiltonian employs the tight-binding parameters of an sp3 orbital basis containing both 1st and 2nd nearest-neighbor interaction terms fit to c-Si band structure. Averaged LDOS of atoms with various bond angle distortions are calculated in order to demonstrate the relationship between the standard deviation in bond angle and the width of the defect states. The CBLM is also used to determine the extent of the valence band tails as a function of the standard deviation in bond angle. In addition, the LDOS of clusters with 2 dangling bonds are examined to determine the degree that their energy levels split due to their interaction with each other.

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