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In a recent paper [Cáceres MO, Comments on wave-like propagation with binary disorder. J. Stat. Phys. 2021;182(36):doi.org/10.1007/s10955-021-02699-0.], the evolution of a wave-like front perturbed by space-correlated disorder was studied. In addition, the generic solution of the field mean-value was presented as a series expansion in Terwiel's cumulants operators. This infinite series cuts due to the algebra of naked Terwiel's cumulants when these cumulants are associated to a space exponential-correlated symmetric binary disorder. We apply an equivalent approach to study the dispersion-relation for 1D surface gravity waves propagating on an irregular floor. The theory is based on the study of the mean-value of plane-wave-like Fourier modes for the propagation and damping of surface waves on a random bottom. [ABSTRACT FROM AUTHOR]

The results of studies of magnetoresistance for GaAs filamentous crystals doped with tellurium admixture to a concentration of 2·1017 сm−3, in the temperature range 4.2–60 K and in the magnetic field ranges 0–14 T are presented. The GaAs filamentary crystal magnetoresistance has shown a sharp positive jump at a low magnetic field (up to 0.2 T) at a temperature near 4.2 K, while at higher magnetic field inductions linear behavior of magnetoresistance occurs. The low field magnetoresistance is discussed in the framework of weak localization of charge carriers due to their spin-orbit exchange interaction. The high-field linear magnetoresistance is connected with electron-electron interaction. [ABSTRACT FROM AUTHOR]

We characterize the effect of ferromagnetic nickel nanoparticles (size ∼ 6   n m ) on the magnetotransport properties of chemical-vapor-deposited (CVD) graphene. The nanoparticles were formed by thermal annealing of a thin Ni film evaporated on top of a graphene ribbon. The magnetoresistance was measured while sweeping the magnetic field at different temperatures, and compared against measurements performed on pristine graphene. Our results show that, in the presence of Ni nanoparticles, the usually observed zero-field peak of resistivity produced by weak localization is widely suppressed (by a factor of ∼3), most likely due to the reduction of the dephasing time as a consequence of the increase in magnetic scattering. On the other hand, the high-field magnetoresistance is amplified by the contribution of a large effective interaction field. The results are discussed in terms of a local exchange coupling, J ∼ 6   m e V , between the graphene π electrons and the 3d magnetic moment of nickel. Interestingly, this magnetic coupling does not affect the intrinsic transport parameters of graphene, such as the mobility and transport scattering rate, which remain the same with and without Ni nanoparticles, indicating that the changes in the magnetotransport properties have a purely magnetic origin. [ABSTRACT FROM AUTHOR]

The impact of bismuth incorporation into the epitaxial layer of a (Ga,Mn)As dilute ferromagnetic semiconductor on its magnetic and electromagnetic properties is studied in very thin layers of quaternary (Ga,Mn)(Bi,As) compound grown on a GaAs substrate under a compressive misfit strain. An addition of a small atomic fraction of 1% Bi atoms, substituting As atoms in the layer, predominantly enhances the spin–orbit coupling strength in its valence band. The presence of bismuth results in a small decrease in the ferromagnetic Curie temperature and a distinct increase in the coercive fields. On the other hand, the Bi incorporation into the layer strongly enhances the magnitude of negative magnetoresistance without affecting the hole concentration in the layer. The negative magnetoresistance is interpreted in terms of the suppression of weak localization in a magnetic field. Application of the weak-localization theory for two-dimensional ferromagnets by Dugaev et al. to the experimental magnetoresistance results indicates that the decrease in spin–orbit scattering length accounts for the enhanced magnetoresistance in (Ga,Mn)(Bi,As). [ABSTRACT FROM AUTHOR]

The magneto-quantum and quantum interference effects in a two-dimensional gas of p-type charge carriers are studied for three quantum wells made of practically pure germanium in a Si0.6Ge0.4/Si0.2Ge0.8/Si0.6Ge0.4 heterostructure. The quantum well widths were 8 nm for sample I, 19.5 nm for sample II, and 25.6 nm for sample III. The dependences of resistance on the magnetic field for all samples exhibit Shubnikov–de Haas oscillations. Their analysis made it possible to calculate the kinetic characteristics of charge carriers for the cases of one (sample I) and two occupied subbands (samples II and III). In the region of weak magnetic fields (B < 0.1 T), the effect of weak localization of holes was revealed, which determines the negative magnetoresistance and the increase in resistance with decreasing temperature. The manifestation of the charge carriers interaction effect at various temperatures and magnetic fields is discovered and analyzed. A transition from the diffusion mode of manifestation of the quantum correction to the intermediate, and then to the ballistic mode is observed. In all regions, the behavior of the quantum correction due to the charge carriers interaction effect is in good agreement with modern theoretical predictions. The temperature dependences of the hole-phonon relaxation time are calculated. In weak magnetic fields, with an increase in the temperature of the 2D system, a transition from the "partial inelasticity" mode, characterized by the dependence τ h ph − 1 ∝ T 2 , to the small-angle scattering mode, described by the relation τ h ph − 1 ∝ T 5 , takes place. In stronger magnetic fields for samples with two occupied subbands, the dependence τ h ph − 1 ∝ T 3 was observed. Possible explanations for this dependence are presented. [ABSTRACT FROM AUTHOR]

This paper presents low-temperature measurements of magnetoresistivity in heavily doped n-type GaN grown by basic GaN growth technologies: molecular beam epitaxy, metal-organic vapor phase epitaxy, halide vapor phase epitaxy and ammonothermal. Additionally, GaN crystallized by High Nitrogen Pressure Solution method was also examined. It was found that all the samples under study exhibited negative magnetoresistivity at a low temperature (10 K < T < 50 K) and for some samples this effect was observed up to 100 K. This negative magnetoresistivity effect is analyzed in the frame of the weak localization phenomena in the case of three-dimensional electron gas in a highly doped semiconductor. This analysis allows for determining the phasing coherence time τφ for heavily doped n-type GaN. The obtained τφ value is proportional to T−1.34, indicating that the electron–electron interaction is the main dephasing mechanism for the free carriers. [ABSTRACT FROM AUTHOR]

The brilliant white appearance of ultrathin scattering media with low refractive index contrast and the underlying radiative transport phenomena fascinate scientists for more than a decade. Examples of such systems are the scales of beetles of the genus Cyphochilus, photonic network structures or disordered Bragg stacks (DBS). While previous studies relate the highly efficient scattering in the scales to the anisotropy of the intra‐scale network and diffusive light transport, the coherent radiation propagation dynamics remains unaccounted for. Here, the identification of different coherent light transport regimes using time and spatially resolved coherent light scattering spectroscopy is shown. At least 20% of the collected scattered light originates from weakly localized random photonic modes, in contrast to solely diffusive light transport assumed to date. The identification of this significant role of weak localization in ultrathin brilliant scattering media establishes a new design paradigm for efficient scattering optical materials. [ABSTRACT FROM AUTHOR]

The recent development of subwavelength photonic and phononic crystals shows the possibility of controlling wave propagation at deep subwavelength scales. Subwavelength bandgap phononic crystals are typically created using a periodic arrangement of subwavelength resonators, in our case small gas bubbles in a liquid. In this work, a waveguide is created by modifying the sizes of the bubbles along a line in a dilute two-dimensional bubbly crystal, thereby creating a line defect. Our aim is to prove that the line defect indeed acts as a waveguide; waves of certain frequencies will be localized to, and guided along, the line defect. The key result is an original formula for the frequencies of the defect modes. Moreover, these frequencies are numerically computed using the multipole method, which numerically illustrates our main results. [ABSTRACT FROM AUTHOR]

We calculate the spectral statistics of the Kramersâ€"Weyl Hamiltonian H = v âˆ' α σ α  sin  p α + tσ 0âˆ' α cos  p α in a chaotic quantum dot. The Hamiltonian has symplectic time-reversal symmetry (H is invariant when spin σ α and momentum p α both change sign), and yet for small t the level spacing distribution P (s) ∝ s β follows the β = 1 orthogonal ensemble instead of the β = 4 symplectic ensemble. We identify a supercell symmetry of H that explains this finding. The supercell symmetry is broken by the spin-independent hopping energy ∝ t  cos  p, which induces a transition from β = 1 to β = 4 statistics that shows up in the conductance as a transition from weak localization to weak antilocalization. [ABSTRACT FROM AUTHOR]

Gallium nitride nanowire and nanorod substrates are prospective platforms allowing to control the local strain distribution in graphene films on top of them, resulting in an induction of pseudomagnetic fields. AFM measurements performed in a HybriD mode complemented by SEM allow for a detailed visualization of the strain distribution on graphene surface. Graphene in direct contact with supporting regions is tensile strained, while graphene located in-between is characterized by lower strain. Characteristic tensile strained wrinkles also appear in the areas between the supporting regions. A positive correlation between strain gradient and distances between borders of supporting regions is observed. These results are confirmed by analysis of the Raman D' band intensity, which is affected by an enhancement of intravalley scattering. Furthermore, scanning tunneling spectroscopy shows a local modification of the density of states near the graphene wrinkle and weak localization measurements indicate the enhancement of pseudomagnetic field-induced scattering. Therefore, we show that nanowire and nanorod substrates provide strain engineering and induction of pseudomagnetic fields in graphene. The control of graphene morphology by modification of distances between supporting regions is promising for both further fundamental research and the exploration of innovative ways to fabricate pseudomagnetic field-based devices like sensors or filters. [Display omitted] [ABSTRACT FROM AUTHOR]

Two-dimensional layered carbon materials such as graphene constructed by sp 2 hybridization have raised considerable interest due to their large, non-saturating magnetoresistance. As a new sp - sp 2 hybridization structure layered carbon material, the transport performance of graphdiyne has been founded comparable with graphene, while the magnetoresistance remains to be clarified. In this work, we developed a modified non-transferred graphdiyne film synthesized method and studied its magnetoresistance effect. We observed an unexpected temperature-dependent crossover between positive and negative magnetoresistance in graphdiyne film. The film shows negative magnetoresistance at 5–19 K, the maximum intensity of the negative magnetoresistance was about 150% at 5 K under 3 T magnetic field. It presents positive magnetoresistance at 19–21 K under 3 T magnetic field, the magnetoresistance value reached 150% at 20 K. The mechanism of crossover positive and negative magnetoresistance originates from a superposition of the magnetic polaron model and weak localization. [Display omitted] ● Developed a modified non-transferred graphdiyne film synthesis method grown on an arbitrary substrate. ● Crossover positive and negative magnetoresistance was observed in graphdiyne film. ● Graphdiyne film presents maximum value of 150% in positive magnetoresistance (PMR), and 150% in negative magnetoresistance. [ABSTRACT FROM AUTHOR]

It was studied the electrical magnetoresistance of nickel-and boron-doped filamentary silicon crystals in which a metal-insulator transition is observed. A giant magnetoresistance reaches up to 280% in the Si whiskers with doping concentration of boron р300K = 5⋅1018 cm−3 in the magnetic fields with induction up to 14 T at temperature 4.2 K. Peculiarities of magnetoresistance at low temperatures were shown to be caused by "core-shell" structure of crystals. A giant magnetoresistance nature was considered within quantum magnetoresistance model. The analysis was performed to determine the critical field of transition from classical parabolic magnetoresistance to quantum magnetoresistance, realized in the near-surface region of the crystal. The silicon whiskers were used for design of magnetic field sensors. [ABSTRACT FROM AUTHOR]

We report the deposition of epitaxial SrHfO 3 thin films on a SrTiO 3 (001) substrate in different substrate temperatures by using a pulsed laser deposition (PLD) method. We carried out X-ray diffraction (XRD), X-ray reflectivity (XRR), reciprocal space mapping (RSM), atomic force microscopy (AFM), resistivity, and Hall measurements to examine the crystallinity, morphology and electrical properties of these films. All films showed smooth and uniform morphology with small root mean square (RMS) roughness. While the SrHfO 3 sample grown at 750 °C is metallic, the films deposited at 600 °C, 650 °C, and 700 °C show an upturn at low temperatures. The temperature dependence of the metallic parts was analyzed based on the parallel resistor model that includes resistivity saturation. On the other hand, the low-temperature upturn was found to be well described by a weak localization mechanism. We also observed the possible emergence of non-Fermi liquid behavior when the upturn disappeared. All SrHfO 3 films have p-type charge carriers. Image 1 • High quality SrHfO 3 thin films grown on a SrTiO 3 (001) using the pulsed laser deposition method. • All thin films have metallic behavior at high temperature and possess the p-type charge carrier. • SrHfO 3 thin films have resistivity upturns at low temperatures, which are accounted for by localization mechanism. [ABSTRACT FROM AUTHOR]

The resistivity and magnetoresistance of multi-walled carbon nanotubes with different degrees of structural perfection in the temperature interval from 4.2 K to 293 K and in the magnetic field up to 2 T are investigated. The revealed anomalies of the temperature and field dependences of resistivity of multi-walled carbon nanotubes are analyzed in the terms of charge carrier's weak localization and interaction effects for two-dimensional systems. For carbon nanotubes with different degrees of structural perfection diffusion coefficient, charge carrier's interaction parameter and the value of the Fermi energy are estimated. It is shown that the anomalies found in the resistivity and magnetoresistance for the defective multi-walled carbon nanotubes are related with the manifestation of the weak localization effect, while for the multi-walled carbon nanotubes of the perfect structure these anomalies are explained by the charge carriers interaction effect. [ABSTRACT FROM AUTHOR]

The improved analysis of carrier transport in the single-layer graphene and hybrid structures like graphene/Co nanoparticles (NPs) and graphene/Co NPs/graphene has been conducted. The temperature and magnetic field dependences of the sheet resistance R Sq (T , B) and/or conductivity σ Sq (T, В) has shown the coexistence of negative (NMR) and positive (PMR) contributions in magnetoresistive effect in all the samples under study. The dependences of R Sq (T, B) and/or σ Sq (T, В) were analyzed in the framework of some combinations of 5 models relating to quantum corrections (QCs) to Drude conductivity theory and different hopping models for variable range hopping (VRH) regimes. It was shown, in particular, that in the region of NMR effect below 75 K and in fields B < (0.5–1) T , σ Sq (T, В) dependences obey the combination of QCs theory (at induction <100 mT) and conduction by coherent hopping over localized states in the VRH regime at T < 20 K. In this case, with the phase breaking time of the wave function it follows the power-like law τφ (Т) ∼ T - p with the exponent p ≈ 1. These dependences also allowed to estimate the values of electron concentration n (T) in the structures studied, which were close to the values in the undoped graphene near the neutrality point. In the region of the PMR effect, the electrical resistance of the structures studied increases linearly with increasing B without saturation. This behavior is often attributed to the presence of structural inhomogeneities in the samples (due to e.g. Co-based nanoparticles) under study, which leads to distortion of the current paths under the action of the Lorentz force arising in a perpendicular magnetic field. [Display omitted] • Sandwich graphene/Co nanoparticles/graphene reveal negative and positive contributions into the sheet magnetoresistance. • Negative contribution is due to low localization interference effects and hopping of coherent electrons over localized states. • Positive contribution increases with magnetic induction without saturation owing to inhomogeneities in sandwich structure. [ABSTRACT FROM AUTHOR]

Highlights • Discovery of electron-diffuson scattering contribution to anomalous Hall effect (AHE). • Only in disordered ferromagnets (FMs) does the weak localization contribute to AHE. • Electron-electron interaction effects do not contribute to AHE in crystalline FMs. • A universal scaling holds between AHE and temperature-dependent part of resistivity. Abstract An exhaustive study of the influence of disorder on anomalous Hall (AH) resistivity ( ρ xy AH ), longitudinal resistivity ( ρ xx ), magnetoresistance and magnetization of Co 2 FeSi (CFS) Heusler alloy thin films of fixed (50 nm) thickness, deposited on Si (1 1 1) substrate, reveals the following. Regardless of the degree of disorder present, the side-jump mechanism gives a dominant contribution to ρ xy AH . A new and novel contribution to both ρ xx and ρ xy AH , characterized by the logarithmic temperature (- lnT) dependence at temperatures below the minimum (T < T min ), exclusive to the amorphous CFS films, originates from the scattering of conduction electrons from the diffusive hydrodynamic modes associated with the longitudinal component of magnetization, called 'diffusons'. The electron-diffuson, e - d , scattering and weak localization (WL) mechanisms compete with the inelastic electron-magnon, e - m , scattering to produce the minimum in ρ xx (T) , whereas the minimum in ρ xy AH (T) is caused by the competing contributions from the e - d and e - m scattering, as WL does not contribute to ρ xy AH . Another novel finding is that the e - d scattering contributions to ρ xy AH (T) and ρ xx (T) scale with each other. In sharp contrast, in crystalline films, enhanced electron-electron Coulomb interaction (EEI), which is basically responsible for the resistivity minimum, does not contribute to ρ xy AH with the result that no minimum in ρ xy AH (T) is observed. The conventional ρ xy AH = f (ρ xx) scaling breaks down completely in the present case. However, when ρ xy AH (T) is corrected for the e - d contribution and ρ xx (T) for both e - d and WL contributions (only EEI) in the amorphous (crystalline) films, the AH coefficient, R A (T) = ρ xy AH (T) / 4 π M s (T) , (calculated from the corrected ρ xy AH and spontaneous magnetization, M s ), perfectly scales with ρ xxT , the temperature-dependent part of the corrected ρ xx , for all the CFS thin films. [ABSTRACT FROM AUTHOR]

Grain boundaries (GBs) in polycrystalline graphene could significantly modulate the physicochemical properties of graphene films, and have attracted intense interest. However, fundamental magnetotransport mechanisms of GBs in bilayer graphene grown by chemical vapour deposition (CVD) are scarcely reported. In this work, we synthesize bilayer graphene bicrystals on polycrystalline Cu foils and measure the electronic properties of such grains as well as of individual graphene grain boundaries. Interestingly, the pronounced metallic character of GB is observed, which is dramatically different from individual grains. Large linear magnetoresistance in graphene bicrystals is observed, which attributes to inhomogeneous charge transport, decorated by quantum interference effects at low temperatures. The measurement data show that individual boundaries between coalesced grains impede electrical transport, suppress the magnetoresistance and enhance intervalley scattering, leading to degradation of electrical performance of CVD graphene. Nevertheless, GBs embedded in a perfect graphene sheet can tune its electronic structure at the nanoscale, act as quasi-one-dimensional metallic wires and can be used as good candidates for strong magnetic field sensors. This work is beneficial to the fundamental understanding of the role of GBs in CVD-grown graphene and opens a potential avenue of application for polycrystalline bilayer graphene in functional devices. The pronounced metallic character of grain boundary is observed in bilayer graphene bicrystals synthesized using the solid-state-source CVD method, which is dramatically different from individual grains. Electrical transport measurements show that individual boundaries between coalesced grains impede electrical transport, suppress the magnetoresistance and enhance intervalley scattering in graphene. Image 1 [ABSTRACT FROM AUTHOR]

Graphical abstract Experimental data transverse magnetoresistance of p-type Si whiskers for different temperatures (1.6–50K) and temperature variation of the phase coherence length (1) and spin-orbit coherence length (2) in p-type Si whiskers. Highlights • The influence of magnetic impurity in microcrystals of Si is studied. • Transport of a boron admixture is associated with a weak localization. • Evaluated the phase coherence length and spin-orbit coherence length. Abstract Transverse magnetoresistance in p-type conductivity Si whiskers with different impurity concentration that correspond to the dielectric side of metal-insulator transition were studied in magnetic fields 0–8 T at low temperatures 1.6 to 50 K. The presence of negative magnetoresistance in Si whiskers with concentration 2 × 1018 cm−3 was observed and associated with weak localization. The obtained parameters of phase coherence length l φ and spin-orbit coherence length l so comprise approximately 45 nm and 750 nm, respectively, at 4.2 K. The parameters obtained for Si whisker indicate the presence of hopping conductivity, orders of magnitude stronger than the parameters obtained for Si _B_ whisker with variable-range conductance, which indicates substantial impact of Ni impurities on the whisker magnetoresistance. [ABSTRACT FROM AUTHOR]

Abstract Topological and thermal disorder complicate the mobility characterization in poly(3,4-ethylenedioxythiophene) systems and presently leaves the exact transport mechanisms not fully understood. Here we show that ac -Hall measured by lock-in amplifier is able to resolve the Hall voltage in semimetallic polymers between room temperature and 32 K. These results are evaluated using an organic random phase model. This accounts for the role of tail states and, particularly, for thermal disorder of molecular semiconductors. We report band mobilities up to 3.7 cm2 V−1 s−1 in semimetallic polymers occurring in delocalized bands that originate from significant electron coherence across the polymer chains. Graphical abstract Image 1 Highlights • Moderate disorder inside semimetallic conducting polymers makes the band widths larger than the random disorder potentials fluctuations. • This effect is used to probe low, but stable Hall voltages in presence of dynamic disorder. • We present an organic phase model to derive temperature-dependent band mobilities. • We demonstrate band mobilities for 3 types of commonplace conducting poly(3,4-ethylene-dixoythiophenes). [ABSTRACT FROM AUTHOR]

Abstract We report on the analysis of weak localization observed in epitaxial films of LaNiO 3-δ deposited coherently on SrTiO 3 (001) substrates using different oxygen pressures, controlling thus the oxygen stoichiometry δ. The structural and transport properties of 10 nm thick LaNiO 3-δ films were investigated. In the films deposited under the lowest oxygen pressures, we observe localization effects at low temperatures, indicating first a high structural quality of the films, and second an influence of the growth conditions on the quantum transport properties of the nickelate. We will discuss the origin as well as the dimensionality of this effect, giving insight into novel and accurate strategies for the design of ultrathin LaNiO 3 electrodes for improved next generation electronics devices. Highlights • The significant effect of oxygen pressure during epitaxial film growth is studied. • The structural, electrical properties and film growth conditions are investigated. • The films deposited at low oxygen pressure exhibits weak localization. • The quantum transport in the nickelate films and their film growth are discussed. [ABSTRACT FROM AUTHOR]

The power spectral density Sv(f) of voltage fluctuations in the Ohmic regime of a system varies with voltage V as Sv(f) ≈ Vβ where β is the bias exponent. The equilibrium resistance fluctuation in a homogeneous system provides β = 2 but in disordered systems, we show that β strongly depends on quenched disorder and temperature and is less than 2 in the Ohmic region. At a fixed temperature, β remains nearly equal to 2 at low disorder and decreases from 2 to 1 with the increase in disorder. Interestingly, similar variation in β is observed with the change in temperature from high to low at a fixed quenched disorder. These two cases favor weak localization in the limit of high disorder or low temperature. Experimental results on manganite compounds indicate that the bias exponent β could be used as a sensible nondestructive parameter to identify the existence of a phase transition evolved during the course of investigation. Remarkable correlations between the electrical transport and the power spectral density Sv(f) are observed and explained with the help of inhomogeneous distribution of currents. The results are also supported by the non‐Gaussian nature of the second spectrum of 1/f noise at different temperatures. [ABSTRACT FROM AUTHOR]

Thermoelectric properties of Nb‐doped MoS2 ((Mo, Nb)S2) ultrathin layers have been experimentally investigated. At temperatures of 300–450 K, these ultrathin layers display p‐type degenerate semiconducting behavior. Because of the carrier scattering and weak localization (WL) of the conduction carriers by random potential originated from stacking faults and edge roughness, electrical resistivity decreases with rising temperature. The lack of change of the Seebeck coefficient with layer thickness suggests that the modulation of spectral conductivity is cancelled, even in the WL condition. The experimentally obtained results are consistent with first principles calculations for the density of state of the pristine MoS2 and (Mo, Nb)S2 monolayer. [ABSTRACT FROM AUTHOR]

In this work, different regions of a graphene device were exposed to a 30 keV helium ion beam creating a series of alternating strips of vacancy-type defects and pristine graphene. From magnetoconductance measurements as function of temperature, density of carriers and density of strips we show that the electron-electron interaction is important to explain the logarithmic quantum corrections to the Drude conductivity in graphene with vacancies. It is known that vacancies in graphene behave as local magnetic moments that interact with the conduction electrons and leads to a logarithmic correction to the conductance through the Kondo effect. However, our work shows that it is necessary to account for the non-homogeneity of the sample to avoid misinterpretations about the Kondo physics due the difficulties in separating the electron-electron interaction from the Kondo effect. [ABSTRACT FROM AUTHOR]

Topological qubits based on Majorana Fermions have the potential to revolutionize the emerging field of quantum computing by making information processing significantly more robust to decoherence. Nanowires are a promising medium for hosting these kinds of qubits, though branched nanowires are needed to perform qubit manipulations. Here we report a gold-free templated growth of III–V nanowires by molecular beam epitaxy using an approach that enables patternable and highly regular branched nanowire arrays on a far greater scale than what has been reported thus far. Our approach relies on the lattice-mismatched growth of InAs on top of defect-free GaAs nanomembranes yielding laterally oriented, low-defect InAs and InGaAs nanowires whose shapes are determined by surface and strain energy minimization. By controlling nanomembrane width and growth time, we demonstrate the formation of compositionally graded nanowires with cross-sections less than 50 nm. Scaling the nanowires below 20 nm leads to the formation of homogeneous InGaAs nanowires, which exhibit phase-coherent, quasi-1D quantum transport as shown by magnetoconductance measurements. These results are an important advance toward scalable topological quantum computing. [ABSTRACT FROM AUTHOR]

Spin-orbit coupling (SOC) plays a crucial role for spintronics applications. Here we present the first demonstration that the Rashba SOC at the SrTiO3-based interfaces is highly tunable by photoinduced charge doping, that is, optical gating. Such optical manipulation is nonvolatile after the removal of the illumination in contrast to conventional electrostatic gating and also erasable via a warming-cooling cycle. Moreover, the SOC evolutions tuned by illuminations with different wavelengths at various gate voltages coincide with each other in different doping regions and collectively form an upward-downward trend curve: In response to the increase of conductivity, the SOC strength first increases and then decreases, which can be attributed to the orbital hybridization of Ti 3d subbands. More strikingly, the optical manipulation is effective enough to tune the interferences of Bloch wave functions from constructive to destructive and therefore to realize a transition from weak localization to weak antilocalization. The present findings pave a way toward the exploration of photoinduced nontrivial quantum states and the design of optically controlled spintronic devices. [ABSTRACT FROM AUTHOR]

Cooperative scattering has been the subject of intense research in the last years. In this article, we discuss the concept of cooperative scattering from a broad perspective. We briefly review the various collective effects that occur when light interacts with an ensemble of atoms. We show that some effects that have been recently discussed in the context of ‘single-photon superradiance’, or cooperative scattering in the linear-optics regime, can also be explained by ‘standard optics’, i.e. using macroscopic quantities such as the susceptibility or the diffusion coefficient. We explain why some collective effects depend on the atomic density, and others on the optical depth. In particular, we show that, for a large and dilute atomic sample driven by a far-detuned laser, the decay of the fluorescence, which exhibits superradiant and subradiant dynamics, depends only on the on-resonance optical depth. We also discuss the link between concepts that are independently studied in the quantum-optics community and in the mesoscopic-physics community. We show that the coupled-dipole model predicts a departure from Ohm’s law for the diffuse light, that incoherent multiple scattering can induce a saturation of fluorescence and we also show the similarity between the weak-localization correction to the diffusion coefficient and the inaccuracy of Lorentz local field correction to the susceptibility. [ABSTRACT FROM PUBLISHER]

The magneto-transport proprieties of silicon nanowires (SiNWs) for various etching time at room temperature has been studied. SiNWs were formed by metal-assisted chemical etching of crystalline silicon in AgNO 3 -based chemical solutions. Scanning electron microscopy (SEM) shows that the SiNWs may have different structures and their lengths depending on the etching time. We found that the electrical conductance and magnetoconductance (MC) effect are extremely depended on the etching time. MC measurements at room temperature revealed a positive MC and this effect is important and it reaches up to 9% at a magnetic field of 0.5 T. The latter effect can be discussed in terms of quasi-one-dimensional (quasi-1D) weak localization (WL) theory. [ABSTRACT FROM AUTHOR]

Transitional metal ditelluride WTe2 has been extensively studied owing to its intriguing physical properties like nonsaturating positive magnetoresistance and being possibly a type-II Weyl semimetal. While surging research activities were devoted to the understanding of its bulk properties, it remains a substantial challenge to explore the pristine physics in atomically thin WTe2. Here, we report a successful synthesis of mono- to few-layer WTe2 via chemical vapor deposition. Using atomically thin WTe2 nanosheets, we discover a previously inaccessible ambipolar behavior that enables the tunability of magnetoconductance of few-layer WTe2 from weak antilocalization to weak localization, revealing a strong electrical field modulation of the spin-orbit interaction under perpendicular magnetic field. These appealing physical properties unveiled in this study clearly identify WTe2 as a promising platform for exotic electronic and spintronic device applications. [ABSTRACT FROM AUTHOR]

Negative magnetoresistance (MR) up to 13% was observed at 2 K under the magnetic field of 7 T in amorphous carbon thin films synthesized by chemical vapor deposition. No tendency of saturation of MR is observed up to the magnetic field of 7 T. Shift of structural morphology from disordered amorphous carbon to ordered graphitic like carbon was studied by using Raman, X-ray Diffraction, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Negative MR effect increases with the increase in structural order. The mechanism of this negative MR could be ascribed to the Weak Localization and Grain Boundary Scattering Conduction depending on the different temperature regimes. [ABSTRACT FROM AUTHOR]

The negative magnetoresistance of thin In 2 O 3 films, obtained by an autowave oxidation reaction, was detected within a temperature range of 4.2–80 K. The magnetoresistance was –1.35% at a temperature of 4.2 K and an external magnetic field of 1 T. A weak localization theory was used to explain the negative magnetoresistance and to determine the phase-coherence length in a temperature range of 4.2–80 K. The phase-coherence length was found to oscillate as the temperatures increased to around 30 K. From the maximum and minimum values of the oscillation of the phase-coherence length, it was suggested that the In 2 O 3 film has two structure characteristic parameters. Transmission electron microscopy showed the structure of the thin In 2 O 3 film to have structural features of a «crystal phase – amorphous phase». It was found that the crystalline phase characteristic size was consistent with the maximum phase-coherence length and the amorphous phase characteristic size was consistent with the minimum phase-coherence length. It has been suggested that the temperature measurements of the magnetoresistance and the theory of weak localization can be used to evaluate the structural features of nanocomposite or nanostructured thin films. [ABSTRACT FROM AUTHOR]

Lanthanum-based manganites LaCaSrAgMnO ( x = 0.1, 0.2, 0.3) doped with both alkaline metal (Ag) and alkaline earth (Ca and Sr) elements are studied. The structural characterization of polycrystalline samples synthesized through low temperature nitrate route confirms orthorhombic structure for all the investigated samples. The morphology of crystal grains shows that the grains are nearly uniform in size and spherical. Electrical resistivity of samples reveal two transition peaks typical of Ag-doped lanthanum-based manganites. Significant room temperature magneto resistivity (MR) is observed for all the samples. MR is found to behave almost linearly with temperature for x = 0.1 sample for different magnetic field strengths in contrast to plateau type behaviour observed for x = 0.3 sample. Standard temperature-dependent resistivity models such as small polaron and variable range hopping are used to fit the resistivity data in the high temperature range. In the low temperature domain, the resistivity data could be fitted to a model which combines electron-electron scattering and weak localization. [ABSTRACT FROM AUTHOR]

We evaluate the spin polarization (Edelstein or inverse spin galvanic effect) and the spin Hall current induced by an applied electric field by including the weak localization corrections for a two-dimensional electron gas. We show that the weak localization effects yield logarithmic corrections to both the spin polarization conductivity relating the spin polarization and the electric field and to the spin Hall angle relating the spin and charge currents. The renormalization of both the spin polarization conductivity and the spin Hall angle combine to produce a zero correction to the total spin Hall conductivity as required by an exact identity. Suggestions for the experimental observation of the effect are given. [ABSTRACT FROM AUTHOR]

Here we report in-situ monitoring of electrical transport properties of graphene subjected to sequential and controlled nitrogen plasma doping. The nitrogen is presumed to be incorporated in to the carbon lattice of graphene by making covalent bonding as observed by the swinging of the sign of the thermopower from (initial) positive to (eventual) negative. Electrical transport properties for nitrogen-doped graphene are believed to be governed by the enhanced scattering due to nitrogen dopants and presence of localized states in the conduction band induced by doping. Our results are well supported by Raman and XPS results. [ABSTRACT FROM AUTHOR]

The resistivity ( ρ) data for RFeAsO compounds (R = Ce, Pr, Nd, Sm), in the temperature ( T) range 35-315 K have been analyzed to identify the dominant scattering mechanisms. Close to the room temperature, the system appears to be a metal with low electron density, and the electron-phonon scattering is the dominant one. At lower temperatures, electron-electron scattering plays an important role. In an intermediate temperature region, unlike metallic system, d ρ/d T is negative; and ρ varies as ln T as in a state of weak localization. We look into the origin of negative d ρ/d T. The analysis of ρ( T) data below the SDW transition temperature shows the presence of electron-electron interaction in addition to a SDW energy gap, and also gives an estimate of the SDW energy gap. [ABSTRACT FROM AUTHOR]

A discrete random medium is an object in the form of a finite volume of a vacuum or a homogeneous material medium filled with quasi-randomly and quasi-uniformly distributed discrete macroscopic impurities called small particles. Such objects are ubiquitous in natural and artificial environments. They are often characterized by analyzing theoretically the results of laboratory, in situ , or remote-sensing measurements of the scattering of light and other electromagnetic radiation. Electromagnetic scattering and absorption by particles can also affect the energy budget of a discrete random medium and hence various ambient physical and chemical processes. In either case electromagnetic scattering must be modeled in terms of appropriate optical observables, i.e., quadratic or bilinear forms in the field that quantify the reading of a relevant optical instrument or the electromagnetic energy budget. It is generally believed that time-harmonic Maxwell’s equations can accurately describe elastic electromagnetic scattering by macroscopic particulate media that change in time much more slowly than the incident electromagnetic field. However, direct solutions of these equations for discrete random media had been impracticable until quite recently. This has led to a widespread use of various phenomenological approaches in situations when their very applicability can be questioned. Recently, however, a new branch of physical optics has emerged wherein electromagnetic scattering by discrete and discretely heterogeneous random media is modeled directly by using analytical or numerically exact computer solutions of the Maxwell equations. Therefore, the main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the Maxwell–Lorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell–Lorentz equations, we trace the development of the first-principles formalism enabling accurate calculations of monochromatic and quasi-monochromatic scattering by static and randomly varying multiparticle groups. We illustrate how this general framework can be coupled with state-of-the-art computer solvers of the Maxwell equations and applied to direct modeling of electromagnetic scattering by representative random multi-particle groups with arbitrary packing densities. This first-principles modeling yields general physical insights unavailable with phenomenological approaches. We discuss how the first-order-scattering approximation, the radiative transfer theory, and the theory of weak localization of electromagnetic waves can be derived as immediate corollaries of the Maxwell equations for very specific and well-defined kinds of particulate medium. These recent developments confirm the mesoscopic origin of the radiative transfer, weak localization, and effective-medium regimes and help evaluate the numerical accuracy of widely used approximate modeling methodologies. [ABSTRACT FROM AUTHOR]

In present work a novel method for the functionalization of carbon nanotubes is proposed. The magnetoresistance of carbon nanotubes specimens in temperature range from 1.6 K up to 85 K and in magnetic field up to 5 T was investigated. It was shown that the proposed functionalization method does not cause any new defects in structure of carbon nanotubes and does not essentially influence the resistivity of nanotubes. It is revealed the appearance of the charge carriers weak localization and interactions effects for as-prepared and functionalized carbon nanotubes. On the basis of the experimental data, the explicit type of temperature dependence of wave function phase relaxation time and Fermi-level energy value for as-prepared and functionalized carbon nanotube are established. [ABSTRACT FROM AUTHOR]

We evaluate the spin polarization (Edelstein or inverse spin galvanic effect) and the spin Hall current induced by an applied electric field by including the weak localization corrections for a two-dimensional electron gas. We show that the weak localization effects yield logarithmic corrections to both the spin polarization conductivity relating the spin polarization and the electric field and to the spin Hall angle relating the spin and charge currents. The renormalization of both the spin polarization conductivity and the spin Hall angle combine to produce a zero correction to the total spin Hall conductivity as required by an exact identity. Suggestions for the experimental observation of the effect are given. [ABSTRACT FROM AUTHOR]

• Sulfur doped g-C 3 N 4 samples by pyrolysis method. • Room temperature ferromagnetism. • Low-temperature positive magnetoresistance due to wave function shrinkage. • Negative magnetoresistance follows the weak localization effect. Generation of superior magnetic property in two-dimensional nanosheets is an important issue in condensed matter physics due to its potential exploitation in the field of Spintronic application. Metal-free ferromagnetism in 2D materials could generate a long spin lifetime due to its s/p electron configuration, which is the key factor for spin transfer. In the present work, we have synthesised 2D graphitic carbon nitride doped with sulfur (S) atom to investigate the magnetic property due to the interaction of the S atom with the lattice of graphitic carbon nitride. Due to S doping, we get a long-range ferromagnetic ordering in our sample, persisting upto room temperature, and the precise control of S concentration can tune the magnetic property of the system. Interestingly, the magnetotransport (MR) study shows a transition from positive MR at low temperature to negative MR at room temperature. The wave function shrinkage model explains the low-temperature positive MR, where the negative MR follows the weak localization effect. Thus, the overall magnetic and electrical response of S doped graphitic carbon nitride makes it a potential candidate for future spintronic application. [ABSTRACT FROM AUTHOR]

The transport properties of Ge-doped single GaN nanowires are investigated, which exhibit a weak localization effect as well as universal conductance fluctuations at low temperatures. By analyzing these quantum interference effects, the electron phase coherence length was determined. Its temperature dependence indicates that in the case of highly doped nanowires electron-electron scattering is the dominant dephasing mechanism, while for the slightly doped nanowires dephasing originates from Nyquist-scattering. The change of the dominant scattering mechanism is attributed to a modification of the carrier confinement caused by the Ge-doping. The results demonstrate that the phase coherence length can be tuned by the donor concentration making Ge-doped GaN nanowires an ideal model system for studying the influence of impurities on quantum-interference effects in mesoscopic and nanoscale systems. [ABSTRACT FROM AUTHOR]

The thickness dependence of anomalous Hall effect in the amorphous CoFeB thin films has been investigated. A dimensional crossover of electron conduction from 2-D to 3-D in weak localization (WL) has been observed when the film is thicker than 8.5 nm. Meanwhile, the scaling of the anomalous Hall conductivity to the longitudinal conductivity at low temperature, \sigma \mathrm{ AH} {\propto } \sigma \mathrm{ xx}^{n} , also shows the same dimensional crossover of the scaling exponent, $n$ , from 2.3 to 1.2. However, the scaling exponent is corrected to 1.58 after subtracting the contribution of WL effect from the conductance, which indicates that the unified theory, {\sigma }_{\mathrm{ AH}} {\propto } ~ {\sigma }_{\mathrm{ xx}}^{1.6} , is still universally verified for the strongly disordered alloys. [ABSTRACT FROM AUTHOR]

We report the electrical conductance and magnetoconductance (MC) effect in n-type porous silicon (PS) layers. The samples show significant positive MC at room temperature and the presence of a memory effect when a perpendicular low static magnetic field is applied (first scan: 0 T → 0.8 T, second scan: 0.8 T → 0 T). We modeled the experimental results in terms of quasi-one-dimensional (quasi-1D) weak localization (WL) theory. From the fit to experimental data we determined some parameters such as the phase coherence length L ϕ , the mean free path l e and the Fermi wave vector k F for different porosities. These results seem to indicate that WL effect at room temperature predominate on these inhomogeneous systems. [ABSTRACT FROM AUTHOR]

We study a weakly disordered 2D electron gas with two bands and a spectral node within the weak-localization approach and compare its results with those of Gaussian fluctuations around the self-consistent Born approximation. The appearance of diffusive modes depends on the type of disorder. In particular, we find for a random gap a diffusive mode only from ladder contributions, whereas for a random scalar potential the diffusive mode is created by ladder and by maximally crossed contributions. The ladder (maximally crossed) contributions correspond to fermionic (bosonic) Gaussian fluctuations. We calculate the conductivity corrections from the density–density Kubo formula and find a good agreement with the experimentally observed V-shape conductivity of graphene. [ABSTRACT FROM AUTHOR]

We report highly anisotropic appearance of the quantum Hall effect (QHE) in epitaxial single-layer graphene grown on a vicinal SiC(0001) substrate. Well-developed QHE with zero resistance manifests itself for the current along the steps, whereas the QHE is obscured by pronounced positive magnetoresistance with quadratic magnetic-field dependence for the current across the steps. The latter, as well as the small slope of the Hall resistance, implies the presence of parallel conduction due to remnant carriers in the SiC substrate, albeit with seeming inconsistency with the zero resistance observed for the former current direction. We interpret the anisotropic behavior by assuming that the parallel conduction is sizable along the steps but is virtually prohibited across the steps. [ABSTRACT FROM AUTHOR]

We present the experimental results of temperature dependent magnetoresistance (MR) and the magnetization studies of iron encapsulated multiwall carbon nanotube (MWCNT)/polyvinyl chloride (PVC) composites with different wt% of MWCNTs. Transmission electron microscopy characterization shows that MWCNTs are encapsulated with rod-shaped iron nanoparticles of aspect ratio of ~3. The MR behavior of 1.9 wt% MWCNT/PVC sample shows dominance of forward scattering and wave function shrinkage whereas, weak localization and electron–electron interactions explain the MR data of higher wt% samples (9.1, 16.6 and 44.4 wt%). The composites of 4.7 and 9.1 wt% exhibit ferromagnetic behavior at all temperatures with room temperature coercivities of ~1036 and 628 Oe, respectively. [ABSTRACT FROM AUTHOR]

The temperature-dependent electronic transport on the superconducting and insulating sides of the superconductor-insulator transition in disordered quasi-two-dimensional textured FeSe thin films is reported. The transition is driven by a perpendicular magnetic field applied to a film with its thickness close to the critical thickness of the thickness-, i.e., disorder-induced transition. The resistance in the superconducting phase might be dominated by thermally assisted flux flow, and in the phase diagram a metallic phase might intervene between the superconducting and insulating state at very low temperatures. In the insulating phase, weak insulating behavior is observed that can be described by weak localization theory of bosons, thus supporting the bosonic description of the superconductor-insulator transition in FeSe thin films. [ABSTRACT FROM AUTHOR]

Beryllium films with thickness from 44 to 470 nm have been grown via direct current magnetron sputtering. The negative magnetoresistance was observed below ∼10 K, which can be well described by the three-dimensional weak localization theory. The extracted dephasing time τ ϕ obeys the temperature-scaling law of τ ϕ − 1 ∝ T p ˜ . The fitting results indicate that the temperature exponent p ˜ increases from 0.8 to 1.7 while increasing film thickness. The physical mechanism behind this phenomenon may be caused by the crossover from Belitz-Wysokinski electron-electron interaction to incomplete drag electron-phonon interaction, or originated from the sole electron-phonon interaction regulated by the thermal phonon dimensionality. Further evidence is required to determine the exact mechanism. • The negative magnetoresistance of the Be films was observed. • The negative magnetoresistance can be described by the three-dimensional weak localization theory. • The extracted dephasing time obeys the temperature power law. • The temperature exponent increases while increasing film thickness. [ABSTRACT FROM AUTHOR]

Keywords: biomimetics; efficient scattering media; multiple scattering; random photonic media; tailored disorder; weak localization EN biomimetics efficient scattering media multiple scattering random photonic media tailored disorder weak localization 1 1 1 09/21/22 20220915 NES 220915 In article number 2200700, Ruben C. R. Pompe, Dominic T. Meiers, and co-workers investigate coherent light scattering in ultra-thin, brilliant white, low refractive index structures, such as the scales of Cyphochilus beetles. The reported findings emphasize coherence effects in random scattering media and provide new routes for tailoring efficient scattering optical materials. Biomimetics, efficient scattering media, multiple scattering, random photonic media, tailored disorder, weak localization. [Extracted from the article]

A charge transfer chelated system containing ferromagnetic metal centers is the ideal system to investigate the magneto-transport and magneto-dielectric effects due to the presence of both electronic as well as magnetic properties and their coupling. Magneto-transport properties in materials are usually studied through dc charge transport under magnetic field. As frequency dependent conductivity is an essential tool to understand the nature of carrier wave, its spatial extension and their mutual interaction, in the present work, we have investigated frequency dependent magneto-transport along with magnetization behavior in [Co 2 (II)-(5-(4-PhMe)-1,3,4-oxadiazole-H + -2-thiolate) 5 ](OAc) 4 metal complex to elucidate the nature of above quantities and their response under magnetic field in the transport property. We have used the existing model for ac conduction incorporating the field dependence to explain the frequency dependent magneto-transport. It is seen that the frequency dependent magneto-transport could be well explained using the existing model for ac conduction. [ABSTRACT FROM AUTHOR]