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Layer and size dependence of thermal conductivity in multilayer graphene nanoribbons  [PDF]
Hai-Yuan Cao,Zhi-Xin Guo,Hongjun Xiang,Xin-Gao Gong
Physics , 2011, DOI: 10.1016/j.physleta.2011.11.016
Abstract: Using non-equilibrium molecular dynamics method(NEMD), we have found that the thermal conductivity of multilayer graphene nanoribbons monotonously decreases with the increase of the number of layers, such behavior can be attributed to the phonon resonance effect of out-of-plane phonon modes. The reduction of thermal conductivity is found to be proportional to the layer size, which is caused by the increase of phonon resonance. Our results are in agreement with recent experiment on dimensional evolution of thermal conductivity in few layer graphene.
Origin of Universal Optical Conductivity and Optical Stacking Sequence Identification in Multilayer Graphene  [PDF]
Hongki Min,A. H. MacDonald
Physics , 2009, DOI: 10.1103/PhysRevLett.103.067402
Abstract: We show that the origin of the universal optical conductivity in a normal $N$-layer graphene multilayer is an emergent chiral symmetry which guarantees that $\sigma(\omega)=N\sigma_{uni}$ in both low and high frequency limits. [$\sigma_{uni}=(\pi/2) e^2/h$]. We use this physics to relate intermediate frequency conductivity trends to qualitative characteristics of the multilayer stacking sequence.
Modulation of the Optical Transmittance in Multilayer Graphene by an Electrical Signal  [PDF]
J. L. Benítez,D. Mendoza
Physics , 2013, DOI: 10.1063/1.4819466
Abstract: The modulation of the optical transmittance in multilayer graphene by means of an electrical signal in the simple configuration of coplanar electrodes is reported. Besides the fundamental frequency of modulation, higher harmonics also appear in the transmitted signal. Modulation is also observed in the optical reflectance. The modulation of the optical properties in multilayer graphene by electrical signals may be useful for the transmission of information by optical means.
Electrical conductivity in graphene with point defects  [PDF]
Yuriy V. Skrypnyk,Vadim M. Loktev
Physics , 2010, DOI: 10.1103/PhysRevB.82.085436
Abstract: The electrical conductivity of graphene containing point defects is studied within the binary alloy model in its dependence on the Fermi level position at the zero temperature. It is found that the minimal conductivity value does not have a universal character and corresponds to the impurity resonance energy rather than to the Dirac point position in the spectrum. The substantial asymmetry of the resulting dependence of the conductivity on the gate voltage magnitude is attributed as well to this same shift of the conductivity minimum to the resonance state energy.
Quantum Size Effect in Conductivity of Multilayer Metal Films  [PDF]
I. V. Ponomarev,A. E. Meyerovich
Physics , 2003, DOI: 10.1103/PhysRevB.67.165411
Abstract: Conductivity of quantized multilayer metal films is analyzed with an emphasis on scattering by rough interlayer interfaces. Three different types of quantum size effect (QSE) in conductivity are predicted. Two of these QSE are similar to those in films with scattering by rough walls. The third type of QSE is unique and is observed only for certain positions of the interface. The corresponding peaks in conductivity are very narrow and high with a finite cutoff which is due only to some other scattering mechanism or the smearing of the interface. There are two classes of these geometric resonances. Some of the resonance positions of the interface are universal and do not depend on the strength of the interface potential while the others are sensitive to this potential. This geometric QSE gradually disappears with an increase in the width of the interlayer potential barrier.
Temperature Dependence of the Electrical Transport Properties of Multilayer Graphene  [PDF]
E. S. Sadki,H. Okazaki,T. Watanabe,T. Yamaguchi,Y. Takano
Physics , 2013,
Abstract: Multilayer graphene (MLG) thin films are deposited on silicon oxide substrates by mechanical exfoliation (or 'scotch-tape method') from Kish graphite. The thickness and number of layers are determined from both Atomic Force Microscopy (AFM) and Raman Spectroscopy. Electrical terminals are deposited on MLGs in a four-probe configuration by electron-beam lithography, gold/titanium thermal evaporation, and lift-off. The electrical resistance is measured from room temperature down to 2 K. The electrical resistance of the MLGs shows an increase with decreasing temperature, and then decreases after reaching a maximum value. These results are compared with recent experimental and theoretical data from the literature.
Evolution of Co/Cu multilayer conductivity during growth: ab intio study  [PDF]
P. Zahn,N. Papanikolaou,F. Erler,I. Mertig
Physics , 2001, DOI: 10.1103/PhysRevB.65.134432
Abstract: We present ab-initio calculations for the in plane conductivity of Co/Cu multilayer slabs. The electronic structure of the multilayer slabs is calculated by means of density functional theory within a screened KKR scheme. Transport properties are described using the Boltzmann equation in relaxation time approximation. We study the change of the conductivity during growth of the multilayer, and we can reproduce the anomalous, non Ohmic, behavior observed experimentally in several multilayer systems. Our results show that this behavior can be explained in terms of the electronic structure of the slab only. No extra assumption for the scattering at the interfaces is necessary. The connection of electronic structure and conductivity during layer-by-layer growth is elucidated by analyzing the layer-projected conductivities.
Ultrapure Multilayer Graphene in Bromine Intercalated Graphite  [PDF]
J. Hwang,J. P. Carbotte,S. Tongay,A. F. Hebard,D. B. Tanner
Physics , 2011, DOI: 10.1103/PhysRevB.84.041410
Abstract: We investigate the optical properties of bromine intercalated highly orientated pyrolytic graphite (Br-HOPG) and provide a novel interpretation of the data. We observe new absorption features below 620 meV which are absent in the absorption spectrum of graphite. Comparing our results with those of theoretical studies on graphite, single and bilayer graphene as well as recent optical studies of multilayer graphene, we conclude that Br-HOPG contains the signatures of ultrapure bilayer, single layer graphene, and graphite. The observed supermetallic conductivity of Br-HOPG is identi?ed with the presence of very high mobility (~ 121,000 cm2V-1s-1 at room temperature and at very high carrier density) multilayer graphene components in our sample. This could provide a new avenue for single and multilayer graphene research.
On the electrical conductivity of plasmas and metals  [PDF]
Basil Crowley
Physics , 2015,
Abstract: Methods for modelling the electrical conductivity of dense plasmas and liquid metals, based upon the well-known Ziman formula, are reviewed from a general perspective, and some earlier inconsistencies relating to its application to finite temperature systems are resolved. A general formula for the conductivity of a Lorentzian two-component plasma in thermal equilibrium is derived from the Lenard-Balescu collision integral in which both energy and momentum exchange between ions and electrons are accounted for. This formula is used as a basis for some generalizations of the Ziman formula, which apply to plasmas of arbitrary degeneracy over a much wider range of conditions. These formulae implicitly include the collective motions of the ions, but neglect the collective motions of the electrons. Detailed consideration of the latter shows that they generally have a small effect on the conductivity. Conditions for the validity of the Ziman formula are derived. The extension of the general theory to arbitrarily low temperatures, where the ion dynamics become dominated by collective effects, in which dynamical ion correlations need to be taken into account, is shown to lead to the well-known Bloch formula. Consideration is given to non-Lorentzian plasmas by explicitly accounting for electron-electron collisions. Corrections to the Lorentzian model in the form of a power series in 1/Z are derived.
The Electrical Conductivity in the Early Universe  [PDF]
Gordon Baym,H. Heiselberg
Physics , 1997, DOI: 10.1103/PhysRevD.56.5254
Abstract: We calculate the electrical conductivity in the early universe at temperatures below as well as above the electroweak vacuum scale, $T_c\simeq 100$GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, $\sigma_{el}\sim T/\alpha\ln(1/\alpha)$, at temperatures well below $T_c$. At temperatures above, $W^\pm$ charge-exchange processes -- analogous to color exchange through gluons in QCD -- effectively stop left-handed charged leptons. However, right-handed leptons can carry current, resulting in $\sigma_{el}/T$ being only a factor $\sim \cos^4\theta_W$ smaller than at temperatures below $T_c$.
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