de Haas–van Alphen Effect and Localized Spin Fluctuations in Dilute Al–Mn Alloys

1971 ◽  
Vol 49 (13) ◽  
pp. 1813-1822 ◽  
Author(s):  
B. E. Paton
Keyword(s):  
Effective Mass ◽  
Localized States ◽  
Spin Fluctuations ◽  
Mass Ratio ◽  
Electron Phonon Interaction ◽  
Impurity Atoms ◽  
Localized State ◽  
Effective Mass Ratio ◽  
Field Modulation ◽  
Impurity Sites

The de Haas–van Alphen effect in dilute alloys of aluminum-manganese has been measured using the field modulation technique at magnetic fields up to 60 kG and temperatures between 1.1 and 4.2 °K. The period, effective mass ratio, and collision parameter of the third zone y orbits were found to increase linearly on alloying. The increase in the collision parameter attributed to the resonant d scattering by the localized states on the impurity atoms was found to be approximately 10 times larger than the increase observed in aluminum alloys with nontransition element impurities. The effective mass ratio was shown to be enhanced by the electron–phonon interaction and by the localized spin fluctuations on the impurity sites. The parameters which describe the localized state were calculated from the experimental results in the framework of a renormalized theory of localized spin fluctuations and were found to be in agreement with similar parameters calculated from other physical properties. The de Haas–van Alphen results are consistent with the conclusion that the localized state of manganese impurities in aluminum are nonmagnetic but strongly enhanced by localized spin fluctuations.

Transport properties of tungsten-doped VO2

1976 ◽  
Vol 54 (4) ◽  
pp. 408-412 ◽  
Author(s):  
J. M. Reyes ◽  
M. Sayer ◽  
R. Chen
Keyword(s):  
Transport Properties ◽  
Effective Mass ◽  
Conduction Band ◽  
Ac Conductivity ◽  
Impurity Content ◽  
Donor Level ◽  
Mass Ratio ◽  
Compensation Ratio ◽  
Dc And Ac Conductivity ◽  
Effective Mass Ratio

Measurements of DC and AC conductivity and thermopower show that VO2: W can be treated as a conventional n-type extrinsic semiconductor with a donor level 0.06–0.08 eV below the conduction band. For samples with an impurity content from 0.67 → 1.70 at.% W, an effective mass ratio m*/m of 65 ± 10 and a compensation ratio of 0.7 ± 0.1 are deduced from conventional semiconductor theory assuming donor exhaustion just below the metal semiconductor transition.

Measurement of the Modeling Parameters for a Maxiflex “B” Springboard

1990 ◽  
Vol 6 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Eric J. Sprigings ◽  
Denise S. Stilling ◽  
L. Gien Watson ◽  
Paul D. Dorotich
Keyword(s):  
Effective Mass ◽  
Spring Stiffness ◽  
Mass Ratio ◽  
Characteristic Modeling ◽  
Effective Mass Ratio ◽  
Local Stiffness

The characteristic modeling parameters (spring stiffness and effective mass ratio) were determined experimentally for a Maxiflex “B” board. The results indicated that the Maxiflex “B” board was substantially less stiff than a Duraflex board. Most of this decrease in stiffness is a result of the added second taper in the Maxiflex “B” board. Calculations, based on theory, revealed that the perforations in the Maxiflex “B” board reduced the local stiffness over the end region of the board by an additional 10%. As a result of its greater compliancy, the Maxiflex board also had an effective mass ratio that was greater than that of the Duraflex. It was clear from these experiments that the acknowledged superiority of the Maxiflex “B” board over the Duraflex could be attributed directly to the increased compliancy found in the Maxiflex “B” board.

Theoretical Modeling of TLD With Different Tank Geometries Using Linear Long Wave Theory

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
X. Deng ◽  
M. J. Tait
Keyword(s):  
Effective Mass ◽  
Virtual Work ◽  
Damping Ratio ◽  
Wave Theory ◽  
Mass Ratio ◽  
Flat Bottom ◽  
Tuned Liquid Dampers ◽  
Long Wave ◽  
Effective Mass Ratio ◽  
Energy Dissipated

This study focuses on the modeling of tuned liquid dampers (TLDs) with triangular-bottom, sloped-bottom, parabolic-bottom, and flat-bottom tanks using the linear long wave theory. The energy dissipated by damping screens is modeled theoretically utilizing the method of virtual work. In this proposed model, only the fundamental sloshing mode is considered, and the assumption of small free surface fluid response amplitude is made. Subsequently, the equivalent mechanical properties including effective mass, natural frequency, and damping ratio of the TLDs, having different tank geometries, are compared. It is found that the normalized effective mass ratio values for a parabolic-bottom tank and a sloped-bottom tank with a sloping angle of 20 deg are larger than the normalized effective mass ratio values for triangular-bottom and flat-bottom tanks. An increase in the normalized effective mass ratio indicates that a greater portion of the water inside the tank participates in the sloshing motion. The derived equivalent mechanical models for the TLD tank geometries considered in this study can be used for the preliminary design of structural-TLD systems.

Phonon renormalization of the electronic effective mass

1969 ◽  
Vol 47 (10) ◽  
pp. 1107-1116 ◽  
Author(s):  
J. P. Carbotte ◽  
R. C. Dynes ◽  
P. N. Trofimenkoff
Keyword(s):  
Effective Mass ◽  
Phonon Dispersion ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Force Constants ◽  
Coupling Constant ◽  
Phonon Dispersion Curves ◽  
Electron Phonon Interaction ◽  
Phonon Renormalization ◽  
Pseudo Potential

We have made detailed first principle calculations of the phonon contribution to the renormalization of the electronic effective mass of a number of simple metals and alloys. The phonon frequencies and polarization vectors are generated from the interatomic force constants for the material. The force constants are taken from a Born – von Kármán analysis of the experimental phonon dispersion curves determined by inelastic neutron scattering. The electron–phonon interaction is treated using pseudo-potential theory which relates the coupling constant to the electron–ion form factor. For a spherical Fermi surface it is then possible to evaluate numerically the expression for the effective mass with no further approximations. We compare the results obtained with previous work when available and with experiment otherwise.

scholarly journals Kagome van-der-Waals Pd3P2S8 with flat band

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Seunghyun Park ◽  
Soonmin Kang ◽  
Haeri Kim ◽  
Ki Hoon Lee ◽  
Pilkwang Kim ◽  
...  
Keyword(s):  
Diamagnetic Susceptibility ◽  
Van Der Waals ◽  
Localized States ◽  
Flat Band ◽  
Two Dimensional ◽  
Kagome Lattice ◽  
Kagomé Lattice ◽  
Localized State ◽  
Low Dimensional ◽  
Important Structure

AbstractWith the advanced investigations into low-dimensional systems, it has become essential to find materials having interesting lattices that can be exfoliated down to monolayer. One particular important structure is a kagome lattice with its potentially diverse and vibrant physics. We report a van-der-Waals kagome lattice material, Pd3P2S8, with several unique properties such as an intriguing flat band. The flat band is shown to arise from a possible compact-localized state of all five 4d orbitals of Pd. The diamagnetic susceptibility is precisely measured to support the calculated susceptibility obtained from the band structure. We further demonstrate that Pd3P2S8 can be exfoliated down to monolayer, which ultimately will allow the possible control of the localized states in this two-dimensional kagome lattice using the electric field gating.

Electron–phonon interaction in P-, As-, and Sb-doped germanium in the intermediate concentration region

1980 ◽  
Vol 58 (9) ◽  
pp. 1268-1274 ◽  
Author(s):  
V. Radhakrishnan ◽  
P. C. Sharma
Keyword(s):  
Thermal Conductivity ◽  
Conduction Band ◽  
Phonon Scattering ◽  
Metallic State ◽  
Deformation Potential ◽  
Concentration Region ◽  
Electron Phonon Interaction ◽  
Impurity Atoms ◽  
Intermediate Concentration ◽  
Electron Phonon Scattering

The electron–phonon scattering, in the analysis of low temperature thermal conductivity of n-type germanium, is studied in the intermediate donor concentration region. At low concentrations, below metal–insulator transition, the donor electrons are bound to the impurity atoms, and at high concentrations they are free in conduction band. The properties in the intermediate concentration are explained by Mikoshiba's "inhomogeneity model". According to this model, the electrons are in a mixed state both in non-metallic and metallic state. The electron concentrations in the non-metallic and metallic regions are calculated for each sample and the theory of both bound electron–phonon scattering and free electron–phonon scattering are applied. This theory of mixed electron–phonon scattering explains the thermal conductivity results of P-, As-, and Sb-doped germanium samples between 1 and 20 K for intermediate donor concentrations from 1.1 × 1017 to 5.6 × 1017 cm−3. The values of density-of-states effective mass are kept constant (= 0.22) without variation with temperature. The values of shear and dilatation-deformation potential constants are obtained from our calculations. The values of shear-deformation potential for the electrons in the bound region are found to be between 14 and 16 eV, while the values of dilatation-deformation potential are between 1 and 3.5 eV for the electrons in the conduction band and these values are in agreement with the experimentally measured values.

Effect of Biquadratic Exchange on Two Magnon States of Heisenberg Ferromagnets: Other Neighbor Exchange

1975 ◽  
Vol 53 (6) ◽  
pp. 637-647 ◽  
Author(s):  
D. A. Pink ◽  
Vijay Sachdeva
Keyword(s):  
Ground State ◽  
Nearest Neighbor ◽  
Ferromagnetic State ◽  
Localized States ◽  
Heisenberg Ferromagnet ◽  
Green Functions ◽  
Localized Modes ◽  
One Dimensional ◽  
Localized State ◽  
Biquadratic Exchange

We have investigated the two magnon localized states of a one dimensional Heisenberg ferromagnet the Hamiltonian of which is made up of nearest neighbor and next nearest neighbor isotropic bilinear and biquadratic exchange terms, and a single ion anisotropy term. We have restricted our choice of parameters so that the ground state at T = 0 is the fully aligned ferromagnetic state and we have used the thermodynamic Green functions where the averages have been evaluated in the ground state so that our results are good for [Formula: see text]. We have evaluated the probabilities of finding two spin deviations a distance n apart when the system is in a localized state described by total wave vector q. We have (a) compared the effects of ferromagnetic and antiferromagnetic next nearest neighbor exchange, (b) found that localized modes can lie below or above the two free magnon band depending upon the sign and magnitude of the biquadratic exchange, (c) found that in certain cases two spin deviations appear to behave like objects interacting only via a soft core, and (d) found that modes can have a large single ion component when the single ion anisotropy is zero.

Electronic modes in carbon nanotubes with single and double impurity sites

2017 ◽  
Vol 31 (29) ◽  
pp. 1750220
Author(s):  
P. G. Komorowski ◽  
M. G. Cottam
Keyword(s):  
Carbon Nanotubes ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Longitudinal Axis ◽  
Binding Model ◽  
Substitutional Impurity ◽  
Impurity Atoms ◽  
Spatial Configurations ◽  
Impurity Sites ◽  
Walled Carbon Nanotubes

A theoretical study of isolated and doubly-clustered impurities is presented for the electronic excitations in a carbon nanotube lattice. Using a matrix operator formalism and a tight-binding model where the interactions between atoms take place via nearest-neighbor hopping, the properties of the excitations are deduced. A geometry consisting of long, single-walled carbon nanotubes is assumed with the defects introduced in the form of substitutional impurity atoms, giving rise to the localized electronic modes of the nanotube as well as the propagating modes of the pure (host) material. The impurities are assumed to be in a low concentration, having the form of either a single, isolated defect or a small cluster of two defects close together. A tridiagonal matrix technique is employed within a Green’s function formalism to obtain the properties of the discrete modes of the system, including their frequencies and localization. The numerical examples show a dependence on the nanotube diameters and on the relative spatial configurations of the impurities. The results contrast with the previous studies of line impurities since there is no translational symmetry along the longitudinal axis of the nanotubes in the present case.

Impact of Grain Boundary Character on Electrical Property in Polycrystalline Silicon

1999 ◽  
Vol 586 ◽  
Author(s):  
Shu Hamada ◽  
Koichi Kawahara ◽  
Sadahiro Tsurekawa ◽  
Tadao Watanabe ◽  
Takashi Sekiguchi
Keyword(s):  
Electrical Activity ◽  
Temperature Dependence ◽  
Grain Boundaries ◽  
Band Gap ◽  
Misorientation Angle ◽  
Polycrystalline Silicon ◽  
Dominant Role ◽  
Localized States ◽  
Localized State ◽  
The Difference

ABSTRACTGrain boundaries in polycrystalline silicon are most likely to generate localized states in band gap. The localized states play a dominant role in determining the performance of solar cells by acting as traps or recombination center of carriers. In the present investigation, the scanning electron microscope - electron channeling pattern(SEM/ECP) method and SEM - electron back scattered diffraction pattern(SEM/EBSD) technique were applied to characterize the grain boundaries in p-type polycrystalline silicon with 99.999%(5N) in purity. Thereafter, temperature dependence of electrical activity of individual grain boundaries was measured by an electron beam induced current(EBIC) technique.It has been found that temperature dependence of EBIC contrast at grain boundaries can change, depending on the misorientation angle the orientation of the boundary plane. The results can be explained by the difference in the position of the localized state within the band gap on the basis of the Shockley-Read-Hall statistics. The {111} ∑3 symmetrical tilt boundary has shallow states, while high ∑ boundaries have deep states. Low angle boundaries reveal high electrical activities. The EBIC contrast at low angle boundaries was found to increase with increasing misorientation angle up to 2° followed by an almost constant value. High electrical activity at low angle boundaries is probably attributed to a stress field of primary dislocations forming low angle boundaries.

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