... dimensions D Schmeltzer†, R Berkovits, M Kaveh and E Kogan Jack and Pearl Resnick Institute of Advanced Technology, Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel Received 30 July 1998 Abstract. ... ( K + 1 K )]... more
... dimensions D Schmeltzer†, R Berkovits, M Kaveh and E Kogan Jack and Pearl Resnick Institute of Advanced Technology, Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel Received 30 July 1998 Abstract. ... ( K + 1 K )] Vn,m dg dl = [1 − K]g ...
Research Interests:
Research Interests:
Abstract Electron-electron interactions are incorporated into the localization problem by treating them as a perturbation and the following points are shown. (i) If σ ' (n - n c)v and v = 1, then the single-particle density of states... more
Abstract Electron-electron interactions are incorporated into the localization problem by treating them as a perturbation and the following points are shown. (i) If σ ' (n - n c)v and v = 1, then the single-particle density of states is given by N(0)∼(n - n c)η with eta; = 1. (ii) If Hartree terms dominate the electron-electron interaction, then v = 1/2. (iii) For v = 1/2 N(0) is non-critical, i.e. η = 0. (iv) A possible classification of the critical exponents of N(0) and σ near the localization transition is suggested in terms of the interplay between exchange and Hartree interactions.
Research Interests:
A further discussion is given of the use of the Kubo-Greenwood formula to obtain the expression σ ∼ e /nξ for the conductivity near a mobility edge, and also of the effect of a change in the density of states on the conductivity in the... more
A further discussion is given of the use of the Kubo-Greenwood formula to obtain the expression σ ∼ e /nξ for the conductivity near a mobility edge, and also of the effect of a change in the density of states on the conductivity in the weak localization case. We give arguments for a continuous transition in weak magnetic fields, and
Research Interests:
A classification of conduction in organic one-dimensional materials at helium temperatures (in the metallic phase) is presented, which is based on the electron-electron coupling constants. A new '4KF' coupling constant is... more
A classification of conduction in organic one-dimensional materials at helium temperatures (in the metallic phase) is presented, which is based on the electron-electron coupling constants. A new '4KF' coupling constant is derived which accounts for the conduction of the new commensurate materials. The temperature dependence of the conductivity is classified according to the magnitude of the transverse overlap integral.
Research Interests:
ABSTRACT
Research Interests:
Weak localization of light has been demonstrated in the propagation properties of electromagnetic waves in random, strongly scattering media.1 The most striking demonstration of weak localization is shown in Fig.1, which shows the... more
Weak localization of light has been demonstrated in the propagation properties of electromagnetic waves in random, strongly scattering media.1 The most striking demonstration of weak localization is shown in Fig.1, which shows the scattered intensity of a laser beam from a solid, diffuse scatterer as a function of backscattered angle. The peak represents an ensemble average of the speckle patterns of the scattered light, obtained by rotating the sample. The nearly two times stronger, narrow, backscattered peak is predicted by weak localization theories2 and is due to the coherent superposition of time reversed loops through the random media.
Research Interests:
Research Interests:
ABSTRACT A new approach has been developed for the determination of the critical conductivity exponent μ and the critical concentration Nc of the metal-insulator transition without extrapolation of the temperature dependence of the... more
ABSTRACT A new approach has been developed for the determination of the critical conductivity exponent μ and the critical concentration Nc of the metal-insulator transition without extrapolation of the temperature dependence of the conductivity σ(T) to T = 0. We propose to replace σ(0) by Δσ(T*) = σN(T*)-σNc(T*) at low T*, where σ(T) = a+bTp,p = 1/2 or 1/3 is observed. Two series of samples of Ge:As and Ge:Sb were investigated. It is shown that μ = 1 for both series. The normalized values of Δσ(T*)/σ̃ merge for Ge:As, Ge:Sb, Si:P, and Si:Sb into a universal line.
Research Interests:
A Reply to the Comment by M. P. Sarachik and S. Bogdanovich.
Research Interests:
ABSTRACT
Research Interests:
The authors generalise the Mooij rule (1973) for disordered metals. They find that the temperature dependence of the conductivity sigma of a disordered metal as a function of temperature must change slope due to diffusion effects, and if... more
The authors generalise the Mooij rule (1973) for disordered metals. They find that the temperature dependence of the conductivity sigma of a disordered metal as a function of temperature must change slope due to diffusion effects, and if interaction effects are included, sigma changes its slope three times. The crossover temperature (if it occurs at high temperatures) from positive to negative d sigma /dT due to diffusion effects varies as C5, where C is the average concentration of impurities or scattering centres. Another crossover temperature which separates electron correlation effects from diffusion effects is predicted. This explains the temperature dependence observed for Ge1-xAux. It is also shown that the non-metallic behaviour of the AC conductivity is accounted for by diffusion effects and there is no need to invoke the concept of a pseudogap due to electron interaction. The negative magnetoresistance follows from the theory for diffusion effects in agreement with the per...
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
Low-temperature electrical transport data for an ambipolar field-effect-transistor based on an undoped GaAs/AlGaAs quantum well. The data supports the Journal of Physics: Condensed Matter article, 'Reappearance of linear hole... more
Low-temperature electrical transport data for an ambipolar field-effect-transistor based on an undoped GaAs/AlGaAs quantum well. The data supports the Journal of Physics: Condensed Matter article, 'Reappearance of linear hole transport in an ambipolar undoped GaAs/AlGaAs quantum well.' The data were collected at the Cavendish Laboratory, University of Cambridge, in the period February 2015 to September 2015.
Research Interests:
The authors propose a new transport mechanism based on variable-range hopping between power-law localised states. It is shown to be the dominant mechanism at low temperatures. They also argue that a diffusive-hopping transition occurs... more
The authors propose a new transport mechanism based on variable-range hopping between power-law localised states. It is shown to be the dominant mechanism at low temperatures. They also argue that a diffusive-hopping transition occurs above the mobility edge at which the negative magnetoresistance is expected to vanish. Recent data on Si inversion layers support the assertion that such a transition exists and the negative magnetoresistance is found to vanish at a temperature of about 0.3K for an electron density n approximately=0.7*1016 m-2, whereas the mobility edge is estimated to occur for n approximately=(0.4-0.5)*1016 m-2. They also examine the possibility of the absence of a mobility edge and study two hopping mechanisms involving exponentially localised states, for n>0.7*1016 m-2. They present evidence that such mechanisms are not involved here and conclude that exponentially localised states cannot exist for n>0.7*1016 m-2. They show that the data are in agreement with the predictions, which follow from the existence of a mobility edge separating exponentially localised states from power-law localised states.
Research Interests:
... For different energies, there are different functions, since S and K change. Moreover, in the regime L > 5, the slope dp/dG is negative. ... The explanation is that once S becomes larger than unity, a diffusive-hopping transition... more
... For different energies, there are different functions, since S and K change. Moreover, in the regime L > 5, the slope dp/dG is negative. ... The explanation is that once S becomes larger than unity, a diffusive-hopping transition occurs (Kaveh 1984). The argument is as follows. ...
Research Interests:
Research Interests:
A method is presented for obtaining the volume derivatives of the phonon frequencies throughout the Brillouin zone for metals having cubic symmetry. The method is based on the interatomic force constants from the two nearest neighbours... more
A method is presented for obtaining the volume derivatives of the phonon frequencies throughout the Brillouin zone for metals having cubic symmetry. The method is based on the interatomic force constants from the two nearest neighbours and contains one free parameter. The resulting volume derivatives are used to calculate the Gruneisen parameters and the constant-volume temperature derivatives of the phonon frequencies. The calculated values are in good agreement with the recent neutron-scattering measurements for rubidium.
Research Interests:
Research Interests:
Page 1. Magnetic-field-induced insulator-quantum Hall-insulator transition in a disordered two-dimensional electron gas This article has been downloaded from IOPscience. Please scroll down to see the full text article. 1994 J. Phys.:... more
Page 1. Magnetic-field-induced insulator-quantum Hall-insulator transition in a disordered two-dimensional electron gas This article has been downloaded from IOPscience. Please scroll down to see the full text article. 1994 J. Phys.: Condens. Matter 6 4763 ...
Research Interests:
The authors use a local scaling approach to calculate the following properties near the Anderson transition: (i) the time-dependent pulse shape of the transmitted wave through a slab; (ii) the wavelength dependence of the... more
The authors use a local scaling approach to calculate the following properties near the Anderson transition: (i) the time-dependent pulse shape of the transmitted wave through a slab; (ii) the wavelength dependence of the intensity-intensity autocorrelation function C( Delta lambda ); (iii) the time dependence of the intensity-intensity autocorrelation function C( Delta t) for dynamic disorder; (iv) the correlation function
Research Interests:
Research Interests:
The scaling theory of conduction has created much interest in the problem of conduction in a disordered system. Basic to this theory is the assumption that a one-parameter scaling function exists. An experimental test of this is presented... more
The scaling theory of conduction has created much interest in the problem of conduction in a disordered system. Basic to this theory is the assumption that a one-parameter scaling function exists. An experimental test of this is presented for two-dimensional transport in silicon inversion layers. The results are found to be inconsistent with such an assumption and the authors conclude that the function does not exist.
Research Interests:
An analysis is presented of the sample dependence of the specific dislocation resistivity rho D/ND of metals. In contrast to the usual assumption, rho D/ND is not taken to be independent of the dislocation density ND present in the... more
An analysis is presented of the sample dependence of the specific dislocation resistivity rho D/ND of metals. In contrast to the usual assumption, rho D/ND is not taken to be independent of the dislocation density ND present in the sample. The ND dependence of rho D/ND arises from the coupling between electron-dislocation scattering and electron-impurity scattering at low (liquid He)
Research Interests:
The diffusion model is extended to the geometry of long thin wires. In the weak localisation limit, the author obtains the same result as that found by perturbation diagrammatic techniques. In the region where perturbation theory is not... more
The diffusion model is extended to the geometry of long thin wires. In the weak localisation limit, the author obtains the same result as that found by perturbation diagrammatic techniques. In the region where perturbation theory is not applicable, it is found that sigma varies as 1//L2 when the length L of the wire is of the order of the
Research Interests:
Research Interests:
Research Interests:
It is shown that there is excellent agreement between the theory and the recent data of Zwart et al. (1983) for the strain dependence of the electron-electron scattering resistivity for dilute CuAg alloys.
ABSTRACT A calculation is presented of the temperature dependence of the electron-phonon scattering contribution to the electrical resistivity of the alkali metals as a function of the dislocation density present in the sample. Explicit... more
ABSTRACT A calculation is presented of the temperature dependence of the electron-phonon scattering contribution to the electrical resistivity of the alkali metals as a function of the dislocation density present in the sample. Explicit account is taken of the partial quenching of phonon drag by phonon-dislocation scattering. The calculated results are compared with the recent low-temperature resistivity data for a strained sample of potassium. Excellent agreement is found between the calculated values and the measured data.
Research Interests:
Research Interests:
Research Interests:
... Pee(T) = Ptot - PO = (l/gtot) - (1/00) (2.19) Note that we have reduced the conductivities to scalars. ... The first term in equation (3.1) is Ake and the second term is A:,. The derivation of the second term Aie was essentially... more
... Pee(T) = Ptot - PO = (l/gtot) - (1/00) (2.19) Note that we have reduced the conductivities to scalars. ... The first term in equation (3.1) is Ake and the second term is A:,. The derivation of the second term Aie was essentially mathematical. ...
Research Interests:
Research Interests:
Research Interests:
The recently observed T4 behaviour for the low-temperature electrical resistivity of Ag is shown to result from the simultaneous presence of electron-phonon scattering and electron-electron scattering. The magnitude of the... more
The recently observed T4 behaviour for the low-temperature electrical resistivity of Ag is shown to result from the simultaneous presence of electron-phonon scattering and electron-electron scattering. The magnitude of the electron-electron scattering term deduced from the data is in excellent agreement with the recent noble metal calculations. Also, the observed deviations from Matthiessen's rule are shown to result from anisotropic electron-dislocation scattering.
The authors solve Maxwell's equations for a medium with a random dielectric constant by an iterative method that takes into account all two-photon processes by summing all the maximal crossed and ladder diagrams. Their analytic... more
The authors solve Maxwell's equations for a medium with a random dielectric constant by an iterative method that takes into account all two-photon processes by summing all the maximal crossed and ladder diagrams. Their analytic solution for the back-scattering intensity I leads to an inverse linear dependence on wavenumber (I varies as 1/Q), in agreement with recent experiments. The shape of the peak preserves the main features that are found by the approach that replaces Maxwell's equations by a diffusion equation but takes into account interference from time-reversed photon trajectories.