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Showing papers on "Mean free path published in 1993"


Journal ArticleDOI
TL;DR: Based on Boltzmann transport theory, an equation of phonon radiative transfer (EPRT) was developed in this paper, where the phonon-scattering mean free path was used to analyze heat transport by lattice vibrations or phonons.
Abstract: Heat conduction in dielectric thin films is a critical issue in the design of electronic devices and packages. Depending on the material properties, there exists a range of film thickness where the Fourier law, used for macroscale heat conduction, cannot be applied. In this microscale regime, heat transport by lattice vibrations or phonons can be analyzed as a radiative transfer problem. Based on Boltzmann transport theory, an equation of phonon radiative transfer (EPRT) is developed. In the acoustically thick limit, ξ L >>1, or the macroscale regime, where the film thickness is much larger than the phonon-scattering mean free path, the EPRT reduces to the Fourier law

831 citations


Journal ArticleDOI
TL;DR: In this article, a microscopic theory is developed for structures S-N-N′ (S is a superconductor, N, N′ are normal metals) with potential barriers at the interfaces.
Abstract: A microscopic theory is developed for structures S-N-N′ (S is a superconductor, N, N′ are normal metals) with potential barriers at the interfaces. The length of the N layer is supposed to be shorter than the energy relaxation length but longer than the mean free path l , and the dirty case is considered ( l is shorter than the coherence length in the N-layer). The differential conductance is calculated for different values of the barrier resistances compared to the resistance of the middle layer. The conductance has an anomaly (a peak) at voltages V Δ due to an enhancement of the proximity effect at low energies (voltages). The anomaly is suppressed by pairbreaking mechanisms. It is shown that the magnetoconductance can be negative or positive depending on the ratio of the barrier resistances and on the voltage. The AC conductance (admittance) has a peak at a frequency ω Δ . At high voltages V ⪢ Δ a transition from an excess current at high barrier transparencies to a deficit current at low barrier transparencies is found in S-N-N′ (S) structures.

175 citations


Journal ArticleDOI
TL;DR: It is found that Coulomb drag is appreciably enhanced by disorder at low temperatures when the mean free path within a layer is comparable to or shorter than the layer separation.
Abstract: We derive and evaluate expressions for the frictional Coulomb drag between disordered two-dimensional electron-gas layers Our derivation is based on the memory-function formalism and the expression for the drag reduces to previously known results in the ballistic limit We find that Coulomb drag is appreciably enhanced by disorder at low temperatures when the mean free path within a layer is comparable to or shorter than the layer separation In high-mobility two-dimensional electron-gas systems, where the drag has been studied experimentally, the effect of disorder on the drag is negligible at attainable temperatures We predict that an enhancement due to disorder and a crossover in the temperature dependence and layer-separation dependence will be observable at low temperatures in moderate- and low-mobility samples

144 citations


Journal ArticleDOI
TL;DR: In this article, a generalized oscillator strength model based on optical and photoelectric data is proposed to compute the mean free paths and stopping powers of electrons in solids for four materials (Al, Si, Cu and Au) and for electrons with energies from 10 eV to 10 keV.
Abstract: Inelastic scattering of electrons in solids is computed from a generalized oscillator strength model based on optical and photoelectric data. The optical oscillator strength is extended into the non-zero momentum transfer region by using free-electron gas dispersion for the weakly bound electrons. The applicability of this method to non-conduction valence electrons and to inner shells is discussed. A different extension method, which reproduces ionization thresholds, is used for inner-shell ionization. The calculations are simplified by using a two-modes model for the Lindhard theory of the free-electron gas. Exchange effects are accounted for by means of a modified Ochkur approximation. Inelastic mean free paths and stopping powers obtained from this optical-data model for four materials (Al, Si, Cu and Au) and for electrons with energies from 10 eV to 10 keV are presented.

106 citations


Journal ArticleDOI
TL;DR: This study relies on ellipsometric spectra from 1.3 to 4.0 eV collected in real time with a multichannel instrument during both thermal evaporation and magnetron sputtering of Al onto SiO 2 substrates at room temperature.
Abstract: We report a comprehensive study of the optical functions of thin-film aluminum from initial nucleation through continuous film growth. This study relies on ellipsometric spectra from 1.3 to 4.0 eV collected in real time with a multichannel instrument during both thermal evaporation and magnetron sputtering of Al onto ${\mathrm{SiO}}_{2}$ substrates at room temperature. The spectra for all films in the particle growth regime can be modeled with a Maxwell-Garnett-type effective medium theory, modified to include dipole interactions between spheroidal particles arranged on a square grid. The dielectric functions of the Al particles themselves, as well as those of continuous films, are interpreted assuming variable relaxation times for both Drude and interband electronic contributions. The relaxation times are determined by a common value of the mean free path, reduced from its bulk film value owing to electron scattering at defects, particle surfaces, and grain boundaries. For all films in the particle regime of growth, i.e., for thicknesses \ensuremath{\sim}50 \AA{}, the deduced relaxation times are independent of thickness (and hence particle size), and are more than an order of magnitude lower than bulk film values. This suggests a defective structure in which electron scattering at internal particle defects limits the relaxation time and determines the particle optical functions. For Al prepared by high-rate evaporation, a transition is observed at a thickness of 55--60 \AA{}, just after continuous film formation. At the transition, the interband electron relaxation time increases abruptly, signaling the development of higher-quality crystalline grains that extend throughout the film thickness. Only after this transition is the (200) parallel-band absorption feature visible in the Al dielectric function at 1.5 eV. For thicknesses g60 \AA{}, the interband relaxation time increases with thickness, providing evidence that grain-boundary scattering is the dominant mechanism controlling the optical properties in the bulk film stage.

84 citations


Journal ArticleDOI
TL;DR: Measurements of frictional drag between adjacent electron gases in double quantum wells provide strong evidence for phonon-mediated electron-electron interactions, pointing to a novel electron scattering mechanism involving virtual-phonon exchange.
Abstract: Measurements of frictional drag between adjacent electron gases in double quantum wells provide strong evidence for phonon-mediated electron-electron interactions. These interactions, which dominate the contribution from simple Coulomb scattering at layer spacings larger than a few hundred A, are between 20 and 100 times stronger than expected for sequential emission and absorption of real phonons. The observed range of the interactions, substantially smaller than the acoustic phonon mean free path, points to a novel electron scattering mechanism involving virtual-phonon exchange.

83 citations


Journal ArticleDOI
TL;DR: In this article, the authors present fits on the intensity and anisotropy time profiles performed with the model of focused transport for 27 energetic particle events observed on one of the Helios spacecraft.
Abstract: For 27 energetic particle events observed on one of the Helios spacecraft we present fits on the intensity and anisotropy time profiles performed with the model of focused transport. The events have local mean free paths λ∥ between 0.02 and ≥1 AU, for most events λ∥ lies within or above the consensus range between 0.08 and 0.3 AU. The propagation in general can be described as focused or diffusive transport, therefore in the majority of events interplanetary scattering plays an important role. Comparing with results from earlier studies we find that scatter-free events can be observed inside 0.5 AU as well as close to 1 AU, therefore extreme scattering properties seem not to be related to radial changes in scattering conditions. In addition, any radial variation in the scattering mean free path seems to be small compared to the event-to-event variations. A comparison of fits on ∼18-MeV protons and ∼1-MeV electrons shows that the scattering mean free path λp of the protons is related to the electron mean free path λe, whereby the average ratio λp/λe is 1.6±0.9. This latter observation has important consequences for our understanding of the underlying scattering mechanism, in particular as it is in contradiction with conventional results from quasi-linear theory.

67 citations


Journal ArticleDOI
TL;DR: The results suggest that there is a strong interaction between the conduction electrons and the intramolecular vibrational modes and also bring into question the assumption that all of the donated charge (three electrons per C60) is itinerant.
Abstract: Crystalline films of C60 with ~1 μm grain size and a preferred [111] texture have been doped with K and Rb to form superconducting compositions that have sharp zero-resistance transitions. The temperature dependence of the resistance above Tc for both K3C60 and Rb3C60 films reveals metallic behavior up to temperatures as high as 520 K without any evidence of saturation. For Rb3C60, electronic mean free paths significantly shorter than nearest-neighbor C60 distances and anomalously high values of the electron-phonon coupling strength are inferred. These results suggest that there is a strong interaction between the conduction electrons and the intramolecular vibrational modes and also bring into question the assumption that all of the donated charge (three electrons per C60) is itinerant.

57 citations


Journal ArticleDOI
TL;DR: The field and current patterns in these two cases, where the currents are perpendicular to the plane of the layers and in which the currents from the spin-up and spin-down electrons do not mix are discussed.
Abstract: While most transport measurements on multilayered structures have been done for currents in the plane of the layers, there is an emerging interest in the geometry where the currents are perpendicular to the plane of the layers. We discuss the field and current patterns in these two cases. For the latter, the elastic mean free path is not a relevant length scale; rather, it is the spin-flip mean free path that is important. In the case of currents perpendicular to the plane of the layers, one must distinguish between models which allow spin mixing of the currents and those in which the currents from the spin-up and spin-down electrons do not mix

53 citations


Journal ArticleDOI
TL;DR: In this paper, the spin-dependent effects of the inelastic mean free path (IMFP) are evident for low-energy electrons passing through magnetized ferromagnetic films caused by a different attenuation within the layer.

53 citations


Journal ArticleDOI
TL;DR: In this paper, the dispersion relation of heavily thermally affected ion cyclotron waves needed in this model is calculated for the first time, and the derived model parameters are used in a quasi-linear calculation of both proton and electron mean free paths.
Abstract: Quasi-linear theory describing charged particle transport in interplanetary space within the framework of a slab turbulence picture was for a long time confronted with the problem that the theoretically predicted mean free path for scattering at magnetic field fluctuations was too small when compared with the corresponding parameter derived from fits to observed intensity and anisotropy profiles of solar energetic particles. The theory up to now has neglected the dispersiveness of some of the scattering plasma waves and the effects resulting from the finite temperature of the plasma through which the particles propagate. We have therefore attempted to give a more realistic model of an observed interplanetary turbulence spectrum. The most simple picture we find requires the dissipation range to be constituted by parallel dispersive whistler, electron and ion cyclotron waves in a warm plasma (β ≈ 1). The dispersion relation of heavily thermally affected ion cyclotron waves needed in this model is calculated for the first time. The model is fitted to the turbulence spectrum measured on June 7, 1980, by ISEE 3 (ICE). The derived model parameters are used in a quasi-linear calculation of both proton and electron mean free paths. As a first step resonance broadening due to wave damping is neglected. The results are compared with typical empirical proton mean free paths and with electron mean free paths obtained from fits to electron intensity and anisotropy profiles observed simultaneously by the same satellite. In both cases the theoretical values seem to be systematically larger than the empirical ones. Thus scattering enhancements by nonlinear or thermal resonance broadening or oblique waves now bear the hope to remove the discrepancy between theory and observation.

Journal ArticleDOI
TL;DR: In this article, particle pitch angle diffusion coefficients and mean free paths of the particles are derived from a power spectral analysis of the turbulence of the magnetic field during the time of the events and compared with results of fits of propagation models to the particle time-intensity and time-anisotropy profiles observed at the same time.
Abstract: Eight solar energetic proton events observed in the inner heliosphere on the spacecraft Helios 1 or 2 are studied. Particle pitch angle diffusion coefficients and mean free paths are derived from a power spectral analysis of the turbulence of the magnetic field during the time of the events. Quasi-linear theory of wave-particle interaction is applied strictly throughout in combination with the slab model of fluctuations. Several points receive special attention: (1) the large difference in scattering conditions from one event to the other, which requires an individual analysis of each event; (2) the selection of the exact stretch of magnetic field data to be analyzed and the influence of this choice on the result; (3) the exclusion of data periods that contain discontinuities and other nonoscillatory structures; and (4) short-scale variations of the overall field fluctuation level, which can be considerable. As a consequence, the mean free paths of the particles are derived from time series of the varying momentary power density spectra as an appropriate average of the scattering conditions (as an average mean free path). These results from the magnetic field spectra are then compared with results of fits of propagation models to the particle time-intensity and time-anisotropy profiles observed at the same time. Of eight such comparisons, half of the cases exhibit for the first time an approximate agreement between the results of the two approaches, particle analysis and magnetic field analysis. The others, however, still show the discrepancy that is cited in the literature. Among the events with good agreement are the two extreme cases in the whole Helios data set, the event of April 11, 1978, Helios 2, with a mean free path from quasi-linear theory of 0.01 AU, and the events of June 7, 1980, Helios 1, with a mean free path from quasi-linear theory of about 0.8 AU at a rigidity of 0.1 GV. This shows not only that quasi-linear theory in a wave and slab model framework is indeed capable of producing correct results under certain conditions if an appropriate case-by-case analysis is conducted, but also that these cases can encompass a wide range of turbulence strengths. Several possibilities for the source of the discrepancy that remains for the other cases, which the theory and the assumptions applied in this work obviously do not explain, are discussed. However, at the present time no definite solution to the problem is obvious.

Journal ArticleDOI
TL;DR: In this paper, the problem of perpendicular transport in magnetic multilayers was treated by starting from the Boltzmann equation formalism and the model was reduced to the macroscopic model first introduced by Johnson and Silsbee when the spin diffusion length is much longer than the mean free path.

Journal ArticleDOI
TL;DR: In this article, the validity of the similarity parameter SIGMA(s)' = SIGMA (1-g), the reduced scattering coefficient, where g is the average cosine of the scattering phase function is investigated.
Abstract: The validity of the similarity parameter SIGMA(s)' = SIGMA(s) (1-g), the reduced scattering coefficient, where g is the average cosine of the scattering phase function is investigated. Attenuation coefficients alpha and diffusion patterns are obtained from solutions of the transport equation for isotropic scattering and Rayleigh-Gans scattering, applied to infinite media. Similarity is studied for the attenuation coefficient alpha, as well as for the Kubelka-Munk absorption and backscattering coefficients in the positive and negative directions, and for predictions of the internal reflection at interfaces. Similarity between solutions of the Boltzmann equation for highly forward scattering and isotropic scattering (g = 0) exist only when SIGMA(a) much less than SIGMA(s) (1 - g). However, because similarity between results, both with g > 0.9, is independent of the value of the absorption coefficient, it is advantageous to simulate highly forward scattering media like biological tissues with g > 0.9, e.g., by Monte Carlo simulations, instead of using isotropic scattering or diffusion theory. Monte Carlo simulations on slabs confirm the deviations from the diffusion approximation and show the behavior near boundaries. Application of similarity may save calculation time in Monte Carlo simulations, because simulation with a lower value for g will increase the mean free path.

Journal ArticleDOI
20 Jun 1993-EPL
TL;DR: In this article, the authors performed a series of measurements of transmission and surface intensity profiles vs. thickness in which the coherent depth of penetration and the surface reflectivities are varied independently.
Abstract: We have performed a series of measurements of transmission and surface intensity profiles vs. thickness in which the coherent depth of penetration and the surface reflectivities are varied independently. The excellent agreement of diffusion theory which includes interfacial coupling in a natural way allows us to determine the domain of validity of the diffusion model and to obtain the first accurate values for the coherent penetration depth and the optical transport mean free path.

Journal ArticleDOI
TL;DR: In this paper, the a-b plane thermal conductivity and the mean free path of each carrier type were calculated as functions of temperature using kinetic theory, the two-fluid model of the superconducting state, and experimental data for the thermal conductivities and electrical resistivity of a single crystal.
Abstract: Electrons and phonons are the carriers of heat in the a-b plane of the high-T[sub c] superconductor YBa[sub 2]Cu[sub 3]O[sub 7]. In the absence of boundary scattering, the a-b plane thermal conductivity and the mean free path of each carrier type are calculated as functions of temperature using kinetic theory, the two-fluid model of the superconducting state, and experimental data for the thermal conductivity and electrical resistivity of a single crystal. The reduction by boundary scattering of the effective a-b plane thermal conductivity along an epitaxial YBa[sub 2]Cu[sub 3]O[sub 7] film is predicted as a function of temperature and film thickness. The size effect on the phonon conductivity dominates over the size effect on the electron conductivity. The predicted electron mean free path is limited by scattering on defects and is in very good agreement with experimental data from infrared spectroscopy. 44 refs., 7 figs.

Journal ArticleDOI
TL;DR: In this paper, magnetroresistance measurements on superconducting single crystals of K3C60 have been reported, including the upper critical field Hc2(T), coherence length ξ, penetration depth λ, scattering time τ, mean free path l, and zero temperature resistivity ϱ(0).

Journal ArticleDOI
TL;DR: In this article, the authors measured the thermal conductivity of single crystals of hexagonal silicon carbide (6H•SiC) of two different electron densities n and showed that virtually all of the heat is conducted by lattice vibrations.
Abstract: We have measured the thermal conductivity κ of single crystals of hexagonal silicon carbide (6H‐SiC) of two different electron densities n The densities are low such that virtually all of the heat is conducted by lattice vibrations At low temperatures the thermal conductivity of both samples varies as T2 and scales with the electron density The calculated phonon mean free path thus varies as T−1 and is consistent with a model of scattering of the heat‐carrying phonons by electrons in an impurity band

Journal ArticleDOI
TL;DR: In this paper, a new radiative transfer theory is developed for stochastically inhomogeneous scattering media, where the three-dimensional shapes and large scale structures of the media are modeled by stochastic interfaces separating regions of different scattering properties.
Abstract: New radiative transfer theory is developed for stochastically inhomogeneous scattering media. The three-dimensional shapes and large scale (compared to the mean free path) structures of the media are modeled by stochastic interfaces separating regions of different scattering properties. The small scale fluctuations are characterized by a pair-correlation function. The radiative transfer equation is extended to include individual scattering and propagation probabilities of a ray for each subregion as well as the probability for a ray to cross the interface between two subregions. The propagation probability is found to depend on the entire preceding path of the ray; the present formulation accounts for the two previous scatterings. A new adding/doubling algorithm is developed to solve this problem numerically. Transmission through a cloud layer and backward scattering seem to be particularly sensitive to inhomogeneities.

Journal ArticleDOI
TL;DR: Experimental determinations of the dependences Δρ(T)/ρ in this temperature range are in good agreement with the correction to the impurity resistivity of a normal metal due to the quantum interference between the electron-phonon and electron-impurity interactions.
Abstract: The temperature dependence of the resistivity p of thin gold films (thickness d=100-400 A) has been measured at T=30 mK-300 K. In a wide temperature range below θ D /15 (θ D is the Debye temperature) Δρ(T)/p is proportional to T 2 and does not depend on the mean free path of electrons. Experimental determinations of the dependences Δρ(T)/ρ in this temperature range are in good agreement with the correction to the impurity resistivity of a normal metal due to the quantum interference between the electron-phonon and electron-impurity interactions

Journal ArticleDOI
TL;DR: In this paper, the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates is investigated, and supersaturation occurs qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor.
Abstract: By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.

Journal ArticleDOI
TL;DR: In this paper, a model which can account for the experimentally observed variations of the giant magnetoresistance in thin magnetic multilayers with mean free path, interface roughness, magnetic layer, and normal layer thickness has been developed.
Abstract: A model which can account for the experimentally observed variations of the giant magnetoresistance in thin magnetic multilayers with mean free path, interface roughness, magnetic layer, and normal layer thickness has been developed. The model requires the existence of quantum-well states within individual layers or groups of layers, depending on the magnetic state of the film. The calculated results are ob tained by the application of quantum size effect transport theory to these individual layers

Journal ArticleDOI
TL;DR: In this paper, the authors present the fluid equations for typical astrophysical plasmas, for the case of no average magnetic field and nonrelativistic flow speeds, in which particular acceleration occurs.
Abstract: We present the fluid equations for typical astrophysical plasmas, for the case of no average magnetic field and nonrelativistic flow speeds, in which particular acceleration occurs. When combined with the particle transport equation presented earlier by Williams, et al., one obtains a fully self-consistent description of particle transport and smooth fluid flow (length scales significantly larger than the mean free path). A presumed scattering law is taken for particles of all energies, and there is a single distribution function as well. This model of the interaction of particle transport, including acceleration, and fluid dynamics is in terms of four unknowns: the fluid velocity vector and the isotropic part of the particle distribution function

Journal ArticleDOI
TL;DR: The accuracy of quantitative XPS analyses using relative sensitivity factors is increased if matrix effects are accounted for in calculations of surface composition, which requires knowledge of the energy dependence of the inelastic mean free path (IMFP) for a given sample as discussed by the authors.
Abstract: The accuracy of quantitative XPS analyses using relative sensitivity factors is increased if matrix effects are accounted for in calculations of surface composition This requires knowledge of the energy dependence of the inelastic mean free path (IMFP) for a given sample It is sufficient for routine analyses to used the IMFP energy dependence averaged over a number of solids A universal energy dependence is found to better expressed by the Bethe equation than an equation of the form λ=aE p , although in both cases the energy dependence is controlled by one parameter

Journal ArticleDOI
TL;DR: The nucleon mean free path in nuclear matter is derived from this effective Lagrangian taking diagrams up to the fourth order into account and the density determined by the RDHF calculation in the local density approximation is made use of.
Abstract: We present a fully self-consistent and relativistic calculation of the nucleon mean free path in nuclear matter and finite nuclei. Starting from the Bonn potential, the Dirac-Brueckner-Hartree-Fock results for nuclear matter are parametrized in terms of an effective [sigma]-[omega] Lagrangian suitable for relativistic density-dependent Hartree-Fock (RDHF) approximation. The nucleon mean free path in nuclear matter is derived from this effective Lagrangian taking diagrams up to the fourth order into account. For nucleon mean free path in finite nuclei, we make use of the density determined by the RDHF calculation in the local density approximation. Our microscopic results are in good agreement with the empirical data and the predictions of the Dirac phenomenology.

Journal ArticleDOI
TL;DR: In this article, the mean free path λ of cosmic-ray particles along the uniform background magnetic field was derived from interplanetary in-situ observations of solar particle events.
Abstract: We use the general Fokker–Planck coefficients derived in the first paper of this series, which describe the interaction of energetic charged particles with weak plasma turbulence in a magnetized plasma, to calculate the mean free path λ of cosmic-ray particles along the uniform background magnetic field. This quantity is a key parameter for confining energetic charged particles in cosmic plasmas, and can be experimentally inferred from interplanetary in-situ observations of solar particle events

Proceedings ArticleDOI
05 Dec 1993
TL;DR: In this article, the injection probability of substrate hot holes in surface channel p-MOS transistors was investigated and the results indicate significantly lower probabilities for holes than for electrons, for comparable electric fields in the oxide and in the substrate.
Abstract: This paper reports the first experimental results on the injection probability of substrate hot holes in surface channel p-MOS transistors The results indicate significantly lower probabilities for holes than for electrons, for comparable electric fields in the oxide and in the substrate From the substrate field dependence of the measured data, and reasonable assumptions for the Si-SiO/sub 2/ energy barrier for holes, we estimate the mean free path to be approximately 40 angstroms at ambient temperature The injection probability of hot electrons has also been determined on state of the art devices, thus extending previously reported data The corresponding hot electron mean free path compares well with the published values >

Book ChapterDOI
01 Jan 1993
TL;DR: The statistics of the depolarization of light by multiple scattering is a complex problem in the regime of Mie scattering and the correlation functions (Stokes intensities) can be entirely determined by studying the loss of memory of both initial linear and circular polarizations as a function of the thickness of a slab (L) in units of the transport mean free path (l*).
Abstract: The statistics of the depolarization of light by multiple scattering is a complex problem in the regime of Mie scattering Nevertheless, the correlation functions (Stokes intensities) can be entirely determined by studying the loss of memory of both initial linear and circular polarizations as a function of the thickness of a slab (L) in units of the transport mean free path (l*)

Journal ArticleDOI
TL;DR: A new energy scale in the dependence of both quantum interference effects on the bias voltage and magnetic field is observed, which agrees well with the level separation estimated for the states in the corresponding closed system.
Abstract: Conductance fluctuations and weak localization in ultrasmall gold bridges with all dimensions smaller than the elastic mean free path have been studied as a function of magnetic field and applied bias voltage. In addition to the well known Thouless energy we observe a new energy scale in the dependence of both quantum interference effects on the bias voltage. This new energy scale agrees well with the level separation estimated for the states in the corresponding closed system.

Journal ArticleDOI
TL;DR: In this article, the dispersion of the free carrier properties is determined by employing electrical and IR reflectivity measurements, in an attempt to probe the band structure of the material but also to lay down the groundwork for the characterization of epitaxial thin films of this material.
Abstract: TlBiSe2 bulk single crystals are grown with an unusually large spread in carrier concentration for the family of compounds of the general type TlAB2 (A:Bi, Sb; B:Te, Se, S) of almost one order of magnitude. This is achieved by varying the growth and annealing conditions. By employing electrical and IR reflectivity measurements the dispersion of the free carrier properties is determined such as the mobility μ, the mean free path l, the ocnductivity σ, and the susceptibility effective mass m in an attempt to probe the band structure of the material but also to lay down the groundwork for the characterization of epitaxial thin films of this material. It is found that TlBiSe2 can be characterized as a narrow gap semiconductor with a non-parabolic conduction band. In addition evidence of a second higher lying conduction band is presented.