Narrow Results

X-ray diffraction patterns of melt-spun Fe-Cu-Nb-Si-B (FINEMET-type) alloys reveal that crystallites of Fe₂Si and Fe₃B phases with average sizes of 15(5) and 20(2) nm are present in the surface layer of thickness ≈ 10 Å and these nanocrystallites occupy 5–10% of the total volume. The results of an elaborate analysis of the high-resolution electrical resistivity data taken in a temperature range from 13 K to 300 K and their discussion in the light of existing theories demonstrates that the enhanced electron–electron interaction (EEI), quantum interference (QI) effects, inelastic electron–phonon scattering, coherent electron–magnon (and/or electron-spin fluctuation) scattering are the main mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron–phonon scattering is the most effective mechanism to destroy phase coherence of electron wavefunctions. The physical quantities such as diffusion constant, density of states at the Fermi level and the phase-breaking time, determined for the first time for the alloys in question, exhibit a systematic variation with the copper concentration.

We investigated the magnetotransport properties of n- and p-type films of Pb_1-xEu_xTe grown by molecular beam epitaxy, with Eu concentrations close to the Metal-Insulator transition. The n-type sample shows a negative magnetoresistance which magnitude increases continually as the temperature is lowered. On the other hand, for the p-type sample, a negative magnetoresistance can be observed only for temperatures below 7 K. Comparing the magnetoresistance of both samples we show that the scattering mechanism should have a different origin.

In this review, we rederive the controversial influence functional approach of Golubev and Zaikin (GZ) for interacting electrons in disordered metals in a way that allows us to show its equivalence, before disorder averaging, to diagrammatic Keldysh perturbation theory. By representing a certain Pauli factor occuring in GZ's effective action in the frequency domain (instead of the time domain, as GZ do), we also achieve a more accurate treatment of recoil effects. With this change, GZ's approach reproduces, in a remarkably simple way, the standard, generally accepted result for the decoherence rate. — The main text and appendices A.1 to A.3 of the present review are comparatively brief, and have been published previously; for convenience, they are included here again (with minor revisions). The bulk of the review is contained in several additional, lengthy appendices containing the relevant technical details.

The results of experimental study of the weak localization phenomenon in 2D system with artificial inhomogeneity of potential relief are presented. It is shown that the shape of the magnetoconductivity curve is determined by the statistics of closed paths. The area distribution function of closed paths has been obtained using the Fourier transformation of the magnetoconductivity curves taken at different temperatures. The experimental results are found in a good agreement with the results of computer simulation.

We here report the manifestation of weak localization effects in the electrical resistivity of TaN(001) films grown on MgO(001) substrates by a pulsed laser deposition technique. These films were characterized by X-ray diffraction and Rutherford backscattering. High precision electrical resistivity measurements were performed on these films in the temperature range 12–300 K. A careful analysis of data showed these films to lie in the weakly localized regime with negative temperature coefficient of resistivity throughout the whole temperature range of study. A crossover from 2D localization at lower temperatures to 3D localization at higher temperatures was observed.

Quantum interference (QI) correction to dynamical conductivity is calculated with the diagrammatic technique in a weakly-disordered two-dimensional (2D) square lattice around half filling, in which the pointlike nonmagnetic impurities are assumed to be substituted randomly for the host atoms. It is found that the conductivity correction is inversely proportional to the frequency for the case of perfectly-nested Fermi surface, resulting from the contribution of diffusive π modes to the QI effect. Such an antilocalization effect is strikingly different from the logarithmic weak-localization correction predicted for 2D free electron systems.

Single-phase metastable α″-niobium nitride thin films have been synthesized on glass substrates by controlled reactive electron beam evaporation technique and are characterized by X-ray diffraction technique. The transport properties down to low temperatures have also been measured. The temperature dependence of resistivity has a minimum at 132 K and shows a remarkable change in the behavior below 25 K. These have been analyzed in the framework of weak localization effects. The analysis shows that the resistance minimum arises on account of three-dimensional weak localization and there is a cross-over to the two-dimensional weak localization regime at lower temperatures.

Low-field magnetoconductivity caused by the quantum interference is studied in the gated 2D quantum well structures with the composition gradient. It is shown that the Dresselhaus mechanism describes well an antilocalization minimum on the conductivity-magnetic field curve.

The model of weak localization in 2D semiconductor structures in the whole range of classically weak magnetic fields in the presence of the Elliot–Yafet spin relaxation has been developed. It was shown that the spin–orbit interaction influences the value of magnetoresistance in small magnetic fields (within diffusion approximation) and when diffusion approximation is no longer valid.

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant -value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.¹ The fitting procedure gives the value of τ/τ_ϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τ_ϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

We present numerical and analytical studies of the crossover between weak antilocalization and weak localization in monolayer graphene and their influence on thermopower. By the use of the recursive Green's function method, we find that these quantum corrections result in an enhancement of thermopower, which can be observed in the resulting magnetic field dependence. This magneto thermopower strongly depends on the size and strength of the impurities as well as on the back gate voltage of the system and the impurity concentration. We show in detail the crossover of these localization effects with these parameters. Using the disorder parameters of the numerical calculation, we find quantitative agreement with the analytical calculations.

In this paper, we reported an obvious weak localization (WL) effect in perpendicular CoFeB sandwiched by Ta and MgO layers. The WL correction to the anomalous Hall effect (AHE) arises when the sheet resistance is larger than 1.5k$\mathrm{\Omega }$. Furthermore, it is found that the mechanism of AHE is strongly related to the characteristic of the granularity in the MgO/CoFeB/Ta thin films. Both skew scattering and side jump mechanisms will give comparable contribution in the high disorder regime.

Stochastic electrodynamics (SED), an alternative theory to quantum phenomena based on laws of classical physics is shortly reviewed and compared with quantum electrodynamics. Experiments supporting the existence of zero-point fluctuating radiation field, the key concept of SED, are discussed. Relation between measurements of the black-body radiation spectrum and noise is analysed to define conditions under which the zero-point component of radiation or noise can be observed. Further, it is shown that stability of weakly localized orbits, measured in disordered solid state systems, can be explained by the presence of zero-point fluctuations of vacuum.

We present numerical and analytical studies of the crossover between weak antilocalization and weak localization in monolayer graphene and their influence on thermopower. By the use of the recursive Green's function method, we find that these quantum corrections result in an enhancement of thermopower, which can be observed in the resulting magnetic field dependence. This magneto thermopower strongly depends on the size and strength of the impurities as well as on the back gate voltage of the system and the impurity concentration. We show in detail the crossover of these localization effects with these parameters. Using the disorder parameters of the numerical calculation, we find quantitative agreement with the analytical calculations.