Showing papers on "Effective mass (solid-state physics) published in 1973"
TL;DR: The precision density measurement in the apparatus described in the chapter is based on the determination of the natural frequency of an electronically excited, mechanical oscillator, its effective mass being composed of its own unknown mass and the well-defined, but also unknown, volume of the sample under investigation.
Abstract: Publisher Summary The partial specific volume of a solute is a characteristic parameter that can be used in investigations of protein associations and changes in conformation, as well as in studies on protein solvent interactions and various other intermolecular interactions. It provides information needed for the determination of particle mass by means of ultracentrifugation and small-angle X-ray scattering. The precision density measurement in the apparatus described in the chapter is based on the determination of the natural frequency of an electronically excited, mechanical oscillator, its effective mass being composed of its own unknown mass and the well-defined, but also unknown, volume of the sample under investigation. To assure that this volume be well defined, the oscillator is made of a hollow, U-shaped glass tube that can be filled with the liquid sample. The mode of vibration is that of a bending-type oscillator. The positions of its vibrating nodes, which in fact determine the limits of the volume of sample taking part in the motion, is kept stable by the abrupt change in the cross-section of the glass tubes.
300 citations
TL;DR: In this paper, a renormalization-group equation for arbitrary momenta is presented, where counterterms are calculated for zero unrenormalized mass and the solutions involve a momentum-dependent effective mass as well as a momentumdependent effective coupling constant.
Abstract: A new set of renormalization-group equations is presented. These equations are based on a renormalization procedure in which counterterms are calculated for zero unrenormalized mass. Unlike the Gell-Mann-Low and Callan-Symanzik equations, they can be solved for arbitrary momenta. The solutions involve a momentum-dependent effective mass as well as a momentum-dependent effective coupling constant. By studying these solutions at large momenta, it can be shown that the nonleading terms discarded by previous authors do, in fact, remain negligible when the perturbation series is summed to all orders if, and only if, the effective mass vanishes at large momentum, which will be the case if a certain anomalous dimension is less than unity, as it is in asymptotically free theories. In this case, the new renormalization-group equations can be used at large momentum to derive not only the leading term, but the first three terms in an asymptotic expansion of any Green's function. These results are also applied to Wilson coefficient functions, and an important cancellation of anomalous dimensions is noted.
291 citations
TL;DR: In this paper, the consequences of the coupling between the charge carriers and the optical phonons are discussed and applied to a wide range of experimental observations in semiconducting and in insulating solids.
Abstract: The properties of charge carriers in solids can be modified greatly by their real and virtual interactions with optical phonons. These effects differ in two particular ways from the changes induced by interactions with acoustic lattice modes. Firstly, those optical modes which interact with carriers are closely monochromatic. Sharply defined structure can therefore appear in many experimental observations, including optical properties, photoconductivity, tunnelling, the magnetoresistance observed under quantum-limit conditions and a range of coupled mode phenomena embracing boht single carriers and plasma modes. Secondly, in materials of a polar nature the coupling of carriers to the optical modes is particularly strong and the resulting scattering probabilities and changes in effective mass can be large. Nevertheless, significant effects produced by the optical modes may be observed in homopolar semiconductors such as silicon and germanium. This article reviews the consequences of the coupling between the carriers and the optical phonons. The theory of such interactions is developed at length and then applied to a wide range of experimental observations in semiconducting and in insulating solids.
143 citations
TL;DR: In this paper, the free carrier reflection in relation to the effective mass anisotropy in NbSe2 has been discussed, as well as the possible existence of two-dimensional excitons.
Abstract: Normal incidence reflectivity spectra using polarized light have been measured with E perpendicular to c as well as E//c for the layer type crystals of transition metal dichalcogenides WS2, WSe2, alpha -MoTe2, NbS2 and NbSe2 at 78 K and 300 K. Reflectivity peaks observed in the spectra of two polarizations are derived from transitions of quite different symmetry and these have been broadly identified using the band structure of single layer MoS2 as the model. A discussion is given for the free carrier reflection in relation to the effective mass anisotropy in NbSe2, as well as for the possible existence of two-dimensional excitons.
116 citations
TL;DR: In this paper, the Brueckner-Bethe theory was applied to normal Fermi liquids and the quasiparticle interaction and physical quantities related to this were calculated.
110 citations
TL;DR: In this article, the ground state of a model exciton-phonon Hamiltonian was studied using variational techniques, and an improved trial function was obtained by studying an exactly soluble problem: an exciton hopping between two sites and coupled to a phonon field.
Abstract: The ground state of a model exciton-phonon Hamiltonian is studied using variational techniques. A single-exciton band is considered in the tight-binding model; the exciton is coupled to Einstein phonons through a short-range linear interaction. We first verify that a variational wave function corresponding to simple displacements of the lattice coordinates (analogous to the Lee-Low-Pines wave function for the polaron) leads to an unphysical result: For strong exciton-phonon coupling the effective mass of the excitons depends discontinuously on the parameters of the Hamiltonian. We obtain an improved trial function by studying an exactly soluble problem: an exciton hopping between two sites and coupled to a phonon field. The new trial function allows distortion of the Gaussian form of the phonon wave function as well as displacement. Analogous trial functions are used to calculate the energy and effective mass for a one-dimensional lattice with nearest-neighbor exciton hopping. The results are a continuous effective mass and a substantial improvement of the ground-state energy over the Lee-Low-Pines trial function. Arguments are given that the qualitative behavior of the ground state is independent of the dimensionality of the lattice, so that the one-dimensional calculation performed here is adequate.
107 citations
TL;DR: In this paper, the effect of disorder-induced valence-conduction band mixing on the conduction-band effective mass in small-band-gap III-V alloys has been analyzed.
Abstract: The conduction-band effective mass in small-band-gap III-V alloys has been observed to be heavier than would be expected from a standard $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$ calculation in the virtual-crystal approximation. Here we analyze the effect of disorder-induced valence-conduction band mixing on this effective mass. It is found that with a consistent set of assumptions for interband and intraband mixing, one can account for the variation of the band gap, the spin-orbit splitting, and the conduction-band mass in these alloys.
99 citations
TL;DR: In this paper, an effective mass approach to the Ginzburg-Landau equations was used to analyze the data in terms of an anisotropic κ and obtained values for the coherence distances and penetration depths parallel and perpendicular to the layers.
Abstract: On small single crystals of 2H NbSe
2
we have measured the temperature and angular dependence ofH
c2 as well as the temperature dependence ofH
c1 close toT
c. Using an effective mass approach to the Ginzburg-Landau equations we have analyzed our data in terms of an anisotropic κ and obtained values for the coherence distances and penetration depths parallel and perpendicular to the layers. The connection between these parameters and normal-state properties is discussed and shown to be more complex than in the isotropic case.
99 citations
TL;DR: In this paper, the authors calculate the tensor of effective mass which has six independent components for three shape degrees of freedom, among them is the reflection asymmetry, and with these mass parameters and the Strutinsky deformation energy the lifetimes for spontaneous fission are calculated in WKB approximation.
90 citations
TL;DR: In this article, the mass enhancement factor for ten transition metals (Zr, Nb, Mo, Ta, W, Re, Rh, Pd, Ir and Pt) was calculated using information available from band structure calculations, neutron scattering experiments and a simple theory of the electron-phonon coupling.
Abstract: Using information available from band structure calculations, neutron scattering experiments and a simple theory of the electron-phonon coupling. The mass enhancement factor lambda is calculated for ten transition metals: Zr, Nb, Mo, Ta, W, Re, Rh, Pd, Ir and Pt. For the superconducting elements the results are in good qualitative and in reasonable quantitative agreement with the empirical values of lambda obtained from data on the superconducting transition temperature. The magnitude of lambda in the nonsuperconducting metals is discussed.
77 citations
TL;DR: In this paper, an analytical formula for the imaginary part of the complex dielectric constant is given for the most important scattering mechanisms in (degenerate) semiconductors.
Abstract: Thin films of In2O3 are prepared by the spraying method. The concentration of charge carriers is changed from about 8×1019 cm−3 to 5×1020 cm−3 by suitable doping with Sn. The optical effective mass is found to depend slightly on carrier concentration. Electrical and optical measurements indicate that electrons are scattered predominantly by charged impurity centres. Structural investigations show that grain boundary scattering can be neglected. The interpretation of the experimental results is mainly based on a paper by von Baltz and Escher, where analytical formulas for the imaginary part of the complex dielectric constant are given for the most important scattering mechanisms in (degenerate) semiconductors.
TL;DR: In this article, the metallic behavior is observed for light polarized parallel to the conducting axis, and an estimate of the dimensionless electron-phonon coupling constant is obtained from the measured value of τ, λ ph ≅1.3.
TL;DR: In this article, the principal optical constants of the germanium telluride (GeTe) system have been obtained by inverting the spectra using the Kramers-Kronig technique.
Abstract: The reflectance spectra of bulk samples of the germanium telluride (GeTe) system have been measured in the wavelength range 13 to 0.2 μm. The principal optical constants of the system have been obtained by inverting the spectra using the Kramers-Kronig technique. Two distinct types of behavior were encountered depending on whether or not a sample exhibited a free carrier absorption peak. Samples rich in germanium lacked such a peak and had optical properties very similar to amorphous GeTe films. Tellurium rich samples always showed a large free carrier peak and from analysis of their optical Constants the effective mass and optical energy gap of the system was obtained. The variation of the effective mass and energy gap with composition (i.e., hole carrier density) is consistent with the existence of two sets of valence-conduction bands in the system. A multiple band model based on experimental and theoretical data is outlined and its parameters are found to be in good agreement with published work.
TL;DR: In this article, the band structure of crystalline CdSb has been calculated by the use of empirical-pseudopotential method in the single space group representation, and it is found that the lowest energy gap of 0.49 eV is indirect one from ∑ 4 to ∑ 1 on this line.
Abstract: The band structure of crystalline CdSb has been calculated by the use of empirical-pseudopotential method in the single space group representation. Calculated band structures shown that both the bottom of the conduction band and the top of the valence band are on the symmetry line [100]. It is found that the lowest energy gap of 0.49 eV is indirect one from ∑ 4 to ∑ 1 on this line. Direct transition gaps are assigned by using the selection rules. The anisotropy of the effective mass at the top of the valence band is such that ( m h * ) a :( m h * ) b :( m h * ) c =1.60:3.35:1.00 and is in good agreement with the determined from the experimental from the experimental results of the Hall mobilities.
TL;DR: In this paper, Landau's theory of Fermi liquid is applied to obtain the quasi-particle parameters of the interacting two-dimensional electrons in the surface inversion layers of silicon.
Abstract: Landau's theory of Fermi liquid is applied to obtain the quasi-particle parameters of the interacting two-dimensional electrons in the surface inversion layers of silicon. The calculated g -factor exhibits a good agreement with the experimental results of Fang and Stiles over a wide range of electron concentration and supports on a firmer ground Janak's original suggestion that the deviation of the g -factor from the bulk value is caused by the exchange interaction among surface electrons. Similar effects on the effective mass are briefly discussed.
TL;DR: In this article, the elastic K−π− scattering has been obtained from a study of the k−π+ system in 15 000 events of the type K−p→K−π −pπ+ at a K− beam momentum of 4.25 GeV/c.
TL;DR: In this article, the optical excitation spectra of Zn, Cd and Ag acceptors in InSb have been measured, and the Zeeman splitting of the spectra is consistent with the identification of the excitations.
TL;DR: In this article, the effect of the polarization of the medium around a quasiparticle was investigated and the main result was that the introduction of a model space does not appreciably change the quasipparticle's effective mass.
TL;DR: In this article, the effective mass components for the L and X valleys are calculated from the band structure and the deformation potential ΞΓL, derived from photoemission data, is large enough that the two-level model appears adequate for calculation of the threshold field.
Abstract: Calculation of the Γ minimum nonparabolicity of InP from the band structure shows that Kane's theory, which has been used in all velocity‐field calculations, underestimates the nonparabolicity and hence causes understimation of the threshold field. The velocity‐field characteristic is predicted to be anisotropic. The effective mass components for the L and X valleys are calculated from the band structure. The deformation potential ΞΓL, derived from photoemission data, is large enough that the two‐level model appears adequate for calculation of the threshold field.
TL;DR: In this article, the energies of 1s and 2s donor levels in Ge as functions of magnetic field were calculated by using variational wave functions, and the results cast some doubt on certain recent transition assignments of Gershenzon and Gol'tsman.
TL;DR: In this article, the authors studied the quantum size effect using the Shockley model of a one-dimensional lattice terminated by arbitrary surface potentials, and the way the energy levels change as the surface potential changes from very high (kappa identical to psi '(0)/ psi (0)= infinity ) to very low ( kappa = 0) is discussed.
Abstract: The quantum size effect is studied, using the Shockley model of a one-dimensional lattice terminated by arbitrary surface potentials. The way the energy levels change as the surface potential changes from very high ( kappa identical to psi '(0)/ psi (0)= infinity ) to very low ( kappa =0) is discussed. Surface states are included in the discussion. For states near a band edge, which for many purposes are the most important states, the eigenvalue equation is simplified. Then the general features of the solutions can be understood analytically. Numerical computation of the solutions is simple if the bulk band structure is known. The wavefunctions and energy levels are found; for sufficiently thick layers they are similar to those in a square well with an effective well depth. The widely used effectively free electron model is accurate for sufficiently thick films, apart from the omission of surface states. However, the convergence to the effectively free electron model is slower if the effective mass is small, and a significant correction is necessary in many practical cases.
TL;DR: The effective mass ratios of the heavy and light holes at the band edge of p-type gallium phosphide have been determined by submillimetre cyclotron resonance at 77 K as discussed by the authors.
TL;DR: In this paper, Fang and Stiles determined the g-factor of conduction electrons in the surface inversion layer on a silicon (100) surface using the tilted magnetic field method.
TL;DR: In this article, the effect of configuration interaction on radiative lifetime is evaluated, and the authors make a variational analysis of configuration interactions and find that the effective mass functions are delocalized and attenuated in the region between the donor and acceptor cores.
TL;DR: The binding energy of an excitonic molecule in which the electron effective mass is light and isotropic and the hole mass is heavy and anisotropic is calculated by a variational method.
Abstract: The binding energy of the excitonic molecule in which the electron effective mass is light and isotropic and the hole mass is heavy and anisotropic is calculated by a variational method. The energy is found to lie between the two values obtained by replacing the anisotropic hole mass by the geometric mean and by the harmonic mean of its components.
TL;DR: In this article, a new approach to pion-nucleus scattering near the first pionnucleon resonance was developed based on the modification of the pion Green function due to isobarhole excitation in the nuclear medium.
TL;DR: In this paper, a review is given of the theoretical investigations of the rotation, in a magnetic field, of the plane of polarization of infrared electromagnetic waves traversing nonmagnetic semiconductors with cubic crystal lattices.
Abstract: A review is given of the theoretical investigations of the rotation, in a magnetic field, of the plane of polarization of infrared electromagnetic waves traversing nonmagnetic semiconductors with cubic crystal lattices. It is shown that in the range of wavelengths corresponding to the interband or intraband optical absorption the Faraday effect can be used to determine the energy gaps, reduced effective masses, and the spectroscopic bandsplitting factor. At longer wavelengths corresponding to the free-carrier absorption the Faraday effect can yield the average effective mass at the Fermi level and the Fermi energy can be found at low temperatures and in strong magnetic fields. Uniaxial deformation of crystals with many-valley bands makes it possible to use the free-carrier Faraday effect in the determination of the mass averaged out over an energy ellipsoid as well as the transverse component of the effective mass. A review is also given of the experimental results published for germanium, silicon, indium antimonide, gallium arsenide, and lead chalcogenides, which are optically isotropic in the absence of an external magnetic field.
TL;DR: In this article, a high resolution magneto-optical study was made on Cu 2 O in the yellow exciton (n ≧3) and oscillatory region of the spectrum at magnetic fields up to 160 kOe.
Abstract: A high resolution magneto-optical study is made on Cu 2 O in the yellow exciton ( n ≧3) and oscillatory region of the spectrum at magnetic fields up to 160 kOe. The shift and splitting of each exciton line observed in the presence of the field are explained primarily in terms of diamagnetic effects on the odd parity levels of a free hydrogen atom. The degeneracy of the p and f levels with same n is lifted in the absence of the field. The magneto-oscillatory spectrum consists of broad main lines accompanied with sharp lines on the higher energy side, which arise from the relative motion within an electron-hole pair. The reduced effective mass for this motion is obtained from the magneto-oscillatory spectrum as 0.38 m. The effective g value for the diamagnetic effect is 0.73 in the exciton as well as in the oscillatory region.
TL;DR: In this article, the Hall coefficient R H and electrical resistivity p of high-purity aluminium and zinc solid solution alloys have been measured as a function of composition at 4·2 and 77°K.
Abstract: The Hall coefficient R H and the electrical resistivity p of high-purity aluminium and aluminium-base zinc solid solution alloys have been measured as a function of composition at 4·2 and 77°K. At both temperatures, RH changes from negative to positive values with increasing zinc contents. The critical points at which R H is zero are 5·2 at. % Zn at 4·2°K and 7·5 at. % Zn at 77°K, respectively. A rigid two-band model has been employed to account quantitatively for the behaviour of R H and p simultaneously. The relaxation times due to both the thermal scattering and the solute atom scattering have been numerically analysed by using experimental data. The impurity relaxation times are shown to obey the Nordheim concentration rule fairly closely. The effective mass ratio m e/m n of the electrons in the third Brillouin zone to the holes in the second zone is estimated to be 0·44.