scholarly journals Electric Field Induced Twisted Bilayer Graphene Infrared Plasmon Spectrum

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2433
Author(s):  
Jizhe Song ◽  
Zhongyuan Zhang ◽  
Naixing Feng ◽  
Jingang Wang
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Valence Band ◽  
Conduction Band ◽  
Bilayer Graphene ◽  
Physical Mechanisms ◽  
Conduction Bands ◽  
Twisted Bilayer Graphene ◽  
The Difference ◽  
Plasmon Spectrum

In this work, we investigate the role of an external electric field in modulating the spectrum and electronic structure behavior of twisted bilayer graphene (TBG) and its physical mechanisms. Through theoretical studies, it is found that the external electric field can drive the relative positions of the conduction band and valence band to some extent. The difference of electric field strength and direction can reduce the original conduction band, and through the Fermi energy level, the band is significantly influenced by the tunable electric field and also increases the density of states of the valence band passing through the Fermi level. Under these two effects, the valence and conduction bands can alternately fold, causing drastic changes in spectrum behavior. In turn, the plasmon spectrum of TBG varies from semiconductor to metal. The dielectric function of TBG can exhibit plasmon resonance in a certain range of infrared.

scholarly journals Conduction Band Engineering of Half-Heusler Thermoelectrics Using Orbital Chemistry

2021 ◽  
Author(s):  
Shuping Guo ◽  
Shashwat Anand ◽  
Madison K. Brod ◽  
Yongsheng Zhang ◽  
G. Jeffrey Snyder
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
High Symmetry ◽  
Electron Configuration ◽  
Band Engineering ◽  
Conduction Bands ◽  
Orbital Phase ◽  
The Difference ◽  
P Type ◽  
Orbital Character

Semiconducting half-Heusler (HH, XYZ) phases are promising thermoelectric materials owing to their versatile electronic properties. Because the valence band of half-Heusler phases benefit from the valence band extrema at several high-symmetry points in the Brillouin zone (BZ), it is possible to engineer better p-type HH materials through band convergence. However, the thermoelectric studies of n-type HH phases have been lagging behind since the conduction band minimum is always at the same high-symmetry point (X) in the BZ, giving the impression that there is little opportunity for band engineering. Here we study the n-type orbital diagram of 69 HHs, and show that there are two competing conduction bands with very different effective masses actually at the same X point in the BZ, which can be engineered to be converged. The two conduction bands are dominated by the d orbitals of X and Y atoms, respectively. The energy offset between the two bands depends on the difference in electron configuration and electronegativity of the X and Y atoms. Based on the orbital phase diagram, we provide the strategy to engineer the conduction band convergence by mixing the HH compounds with the reverse band offsets. We demonstrate the strategy by alloying VCoSn and TaCoSn. The V0.5Ta0.5CoSn mixture presents the high conduction band convergence and corresponding significantly larger density-of-states effective mass than either VCoSn or TaCoSn. Our work indicates that analyzing the orbital character of band edges provides new insight into engineering thermoelectric performance of HH compounds.

Twist in the Tale: Exploring the Dielectric Screening Effect in Twisted Bilayer Graphene

2022 ◽  
Vol 2 ◽  
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Electronic States ◽  
Bilayer Graphene ◽  
Two Dimensional ◽  
Screening Effect ◽  
Dielectric Screening ◽  
Twisted Bilayer Graphene

Although the screening of an external electric field, strongly influences the electronic states of two-dimensional material stack, it is not well understood. Magnetotransport measurements of twisted double bilayer graphene uncovered the screening of atomic layers.

scholarly journals Tuning Electronic Properties of the SiC-GeC Bilayer by External Electric Field: A First-Principles Study

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 309
Author(s):  
Min Luo ◽  
Bin Yu ◽  
Yu-e Xu
Keyword(s):  
Band Structure ◽  
Electric Field ◽  
Fermi Level ◽  
Electronic Properties ◽  
External Electric Field ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
First Principles Calculations ◽  
Direct Bandgap

First-principles calculations were used to investigate the electronic properties of the SiC/GeC nanosheet (the thickness was about 8 Å). With no electric field (E-field), the SiC/GeC nanosheet was shown to have a direct bandgap of 1.90 eV. In the band structure, the valence band of the SiC/GeC nanosheet was mainly made up of C-p, while the conduction band was mainly made up of C-p, Si-p, and Ge-p, respectively. Application of the E-field to the SiC/GeC nanosheet was found to facilitate modulation of the bandgap, regularly reducing it to zero, which was linked to the direction and strength of the E-field. The major bandgap modulation was attributed to the migration of C-p, Si-p, and Ge-p orbitals around the Fermi level. Our conclusions might give some theoretical guidance for the development and application of the SiC/GeC nanosheet.

scholarly journals Electronic Properties of Bilayer Graphene Strongly Coupled to Interlayer Stacking and an External Electric Field

2015 ◽  
Vol 115 (1) ◽  
Author(s):  
Changwon Park ◽  
Junga Ryou ◽  
Suklyun Hong ◽  
Bobby G. Sumpter ◽  
Gunn Kim ◽  
...  
Keyword(s):  
Electric Field ◽  
Electronic Properties ◽  
External Electric Field ◽  
Bilayer Graphene ◽  
Strongly Coupled

Electric Field Effect on NQR in Ferroelectric Materials

1996 ◽  
Vol 51 (5-6) ◽  
pp. 646-650 ◽  
Author(s):  
Jae Kap Jung ◽  
Hae Jin Kim ◽  
Kee Tae Han ◽  
Sung Ho Choh
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Field Effect ◽  
Ferroelectric Materials ◽  
Line Shift ◽  
Electric Field Effect ◽  
Ionic Crystals ◽  
Line Broadening ◽  
Nuclear Site ◽  
The Difference

Abstract The electric field effect on NQR in ferroelectric materials, 93Nb in LiNbO3 and 14N in NaNO2 and SC(NH2)2 , has been investigated at 77 K. In these crystals with single domain, only the line shift due to the external electric field was observed. In the case of NaNO2 powder and a crystal with multi-domains, line broadening was observed in the external electric field. These phenomena can be explained with the fact that the direction of spontaneous polarization in a domain is related to the direction of the applied electric field. The rate of the NQR line-shift due to the electric field is remarkably smaller in mostly ionic crystals, such as LiNbO3 and NaNO2 , than in a molecular crystal such as SC(NH2)2 . This is due to the strong ionic bonding in ionic crystals. Also, the difference of the Stark shift'between NaNO2 and SC(NH2)2 is discussed in terms of the local electric field and polarizability at the resonant nuclear site.

scholarly journals Параметры зонной структуры тонких пленок Bi-=SUB=-1-x-=/SUB=-Sb-=SUB=-x-=/SUB=- (0≤ x≤ 0.15) на подложках с различным температурным расширением

2019 ◽  
Vol 53 (5) ◽  
pp. 616
Author(s):  
А.В. Суслов ◽  
В.М. Грабов ◽  
В.А. Комаров ◽  
Е.В. Демидов ◽  
С.В. Сенкевич ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Valence Band ◽  
Conduction Band ◽  
Chemical Potential ◽  
Plane Deformation ◽  
Charge Carriers ◽  
Galvanomagnetic Properties ◽  
Bismuth Antimony ◽  
The Difference

The report presents the positions of the conductance and valence band extremes in relation to the chemical potential of the thin bismuth–antimony films (from 0 to 15 at% Sb) on substrates with different thermal expansion. The results are based on the galvanomagnetic properties study of thermal deposited thin films. A significant increase in the concentration of charge carriers in films on substrates with a large thermal expansion was found. The results of calculating the valence band and the conduction band positions at 77 K, depending on the thermal expansion coefficient of the substrate used, are presented. The thin films plane deformation caused by the difference in the film and substrate materials thermal expansion leads to a change in the positions of the conduction band and the valence band of the films relative to their positions in a single crystal with corresponding composition

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