Three-dimensional Weak Localization Research Articles

高质量PtP2晶体中的三维弱局域化和负磁阻效应

高质量PtP2晶体中的三维弱局域化和负磁阻效应

Weak localization effect in Zn1−xCdxO/CdO heterostructures

We present a systematic investigation of the morphological and magnetotransport properties of Zn1−xCdxO/CdO heterostructures managing the electronic barrier by changing x values between 0.50 and 0.95. From physical parameters such as roughness and crystallite size obtained through scanning electron microscopy and x-ray diffraction, we established a correlation between the disorder degree and the amplitude of the negative magnetoresistance as well as the nature of the dominating inelastic scattering mechanisms. The magnetoresistance measurements revealed a negative amplitude for all heterostructures, which clearly shows that the weak localization effect is observed in the low temperature range. Applying the three-dimensional weak localization theory (Kawabata 3D), we extract the phase coherence length, and a relatively large value (maximum reaches 135 nm at 4.2 K) is obtained for the Zn0.05Cd0.95O/CdO heterostructure.

Weak localization in beryllium films

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 τϕ obeys the temperature-scaling law of τϕ−1∝Tp˜. 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.

Weak localization and electron-phonon interaction in layered Zintl phase SrIn2P2 single crystal

Recently, the Zintl phase SrIn2P2 single crystal was proposed to be a topological insulator candidate under lattice strain. Here, we report systematic electrical transport studies on the unstrained layered SrIn2P2 single crystals. The resistance presents a minimum value around T c = 136 K and then increases remarkably at low temperature. Distinct negative magnetoresistance below T c, combined with the anomalous resistance, implies the carriers are weak localized at low temperature due to strong quantum coherence. Further analysis based on three-dimensional weak localization (WL) model suggests that the electron-phonon interaction dominates the phase decoherence process. Moreover, Hall measurements indicate that the transport properties are mainly dominated by hole-type carriers, and the WL effect is obviously affected by the carrier transport. These findings not only provide us a promising platform for the fundamental physical research but also open up a new route for exploring the potential electronic applications.

Anisotropic three-dimensional weak localization in ultrananocrystalline diamond films with nitrogen inclusions

We present a study of the structural and electronic properties of ultrananocrystalline diamond films that were modified by adding nitrogen to the gas mixture during chemical vapor deposition growth. Hall bar devices were fabricated from the resulting films to investigate their electrical conduction as a function of both temperature and magnetic field. Through low-temperature magnetoresistance measurements, we present strong evidence that the dominant conduction mechanism in these films can be explained by a combination of three-dimensional weak localization (3DWL) and thermally activated hopping at higher temperatures. An anisotropic 3DWL model is then applied to extract the phase-coherence time as a function of temperature, which shows evidence of a power-law dependence in good agreement with theory.

Electrical transport properties of polycrystalline SnO2 thin films

We study the electrical transport properties of degenerate tin dioxide thin films with thickness larger than 250 nm. Our samples have a rutile structure and the effective mass of electron is 0.31 m0, which is obtained from the variation in optical bandgap. The temperature dependence of the Hall mobility indicates that the ionized impurity scattering is the dominant elastic scattering mechanism for electrons. In the low temperature range, the clear negative magnetoresistivity is observed, which can be attributed to the three-dimensional weak localization (WL) effect. By applying the three-dimensional WL theory, we extracted the electron dephasing length, which decreased on increasing temperature. Unexpectedly, the temperature dependence of the extracted dephasing length is found to be dominated by the electron-electron scattering in the small-energy-transfer process and the electron-phonon scattering has negligible contribution. This can be attributed to the low electron concentration in our samples.

Defect-driven localization crossovers in MBE-grown La-doped SrSnO3 films

Through systematic control of cation stoichiometry using a hybrid molecular beam epitaxy method, we show a crossover from weak to strong localization of electronic carriers in La-doped $\mathrm{SrSn}{\mathrm{O}}_{3}$ films on $\mathrm{LaAl}{\mathrm{O}}_{3}$(001). We demonstrate that substrate-induced dislocations in these films can have a strong influence on the electron phase coherence length resulting in two-dimensional to three-dimensional weak localization crossover. We discuss the correlation between electronic transport, and defects associated with nonstoichiometry and dislocations.

Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1 nm at 50 K to 99.8±3.6 nm at 1.4 K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T−3/4. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

Spin–orbit coupling and weak antilocalization in the thermoelectric material -K2Bi8Se13

We have studied the effect of spin–orbital coupling (SOC) on the electronic transport properties of the thermoelectric material -K2Bi8Se13 via magnetoresistance measurements. We found that the strong SOC in this material results in the weak antilocalization (WAL) effect, which can be described well by a three-dimensional weak localization model. The phase coherence length extracted from theoretical fitting exhibits a power-law temperature dependence, with an exponent around 2.1, indicating that the electron dephasing is governed by electron–transverse phonon interactions. As in topological insulators, the WAL effect in -K2Bi8Se13 can be quenched by magnetic impurities (Mn) but is robust against non-magnetic impurities (Te). Although our magnetotransport studies provide no evidence for topological surface states, our analyses suggest that SOC plays an important role in determining the thermoelectric properties of -K2Bi8Se13.

Intrinsic and precipitate-induced quantum corrections to conductivity in La2/3Sr1/3MnO3thin films

The low-temperature magnetotransport properties of manganite thin films are characterized by the occurrence of resistivity minima, ${\ensuremath{\rho}}_{\mathrm{min}}$, below 30 K whose origin and especially role of disorder has not yet been explored in detail. In order to contribute to the clarification of the physical mechanism giving rise to the resistivity minimum in these systems, an appropriate concentration (3$%$, 6$%$, and 20$%$) of nanoscaled nonmagnetic ZrO${}_{2}$ particles are introduced as a secondary phase into La${}_{2/3}$Sr${}_{1/3}$MnO${}_{3}$ thin films. As the volume density of ZrO${}_{2}$ precipitates increases, the films show a more pronounced resistivity upturn for $T$ ${T}_{\mathrm{min}}$. The measured temperature and magnetic field dependence of the resistivity of our samples is in good agreement with a combination of the theory of three-dimensional weak localization and electron-electron interactions. We show that within this frame the observed features of the scattering-related resistivity minimum at low temperature in correlated electron systems can be explained, including its spin dependence, its scattering parameters, and its variation with increasing nonmagnetic disorder.

WEAK LOCALIZATION EFFECTS IN METASTABLE SUPERSTRUCTURE NIOBIUM NITRIDE

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.

HIGH FIELD MAGNETOCONDUCTIVITY OF IODINE DOPED HELICAL POLYACETYLENE

The effect of interfibrillar interaction on the charge transport of doped polyacetylene is investigated by studying the high field magnetoconductivity of iodine doped helical polyacetylene. The zero-field resistivity ratio, ρ r = ρ(1.2 K )/ρ(300 K ), is comparable to that of stretch-oriented high-density polyacetylene, which indicates the partial alignment of chains inside a polymer fiber. At low magnetic fields, the small negative component of magnetoconductivity was observed and its magnitude increases as the ρ r value increases. In the high field region, the magnetoconductivity is positive and it clearly shows the linear dependence on the magnetic field up to H = 30 T. The linear field dependence of magnetoconductivity is different from what is expected in the three-dimensional weak localization picture. For the same ρ r value samples, the magnitude of negative magnetoconductivity of S-polyacetylene is much bigger than that of R-polyacetylene, which could be attributed to the difference in the degree of helicity determining the strength of interfibrillar interaction.

Structure, Raman scattering, and transport properties of boron-doped graphite

Boron-doped highly oriented graphite films (B-HOGF's) with an atomic fraction of boron from 0.4 up to 2.2 at. % have been prepared from well-crystallized, highly oriented graphite. The effect of boron doping on crystal structure has been investigated in terms of texture observation with a field-emission gun-type scanning electron microscope and by measurements of the x-ray diffraction and Raman scattering. The results indicate that in B-HOGF's, boron atoms substituted in the graphite lattice and induced disorder, which caused the Raman bands related to the disorder in graphite layer planes to appear. For each of the B-HOGF's, the temperature dependence of the resistivity in a range 1.8--300 K has been measured. The Hall coefficient and transverse magnetoresistance have also been measured at 3.0 K in a magnetic field range up to 4 T. The Hall coefficient data indicate that each of the B-HOGF's is a mixed crystal of graphite grains with and without boron atoms. The temperature dependence of the resistivity and field dependence of the transverse magnetoresistance for B-HOGF's show a characteristic that is possibly explained by a three-dimensional weak localization theory proposed by Sugihara Hishiyama, and Kaburagi.

Quantum interference of electrons inTa4Te4Si

Transport properties of single crystalline quasi-one-dimensional fibers of ${\mathrm{Ta}}_{4}{\mathrm{Te}}_{4}\mathrm{Si}$ are studied. The temperature dependence of the resistivity indicates metallic behavior with a residual resistivity ratio of approximately 3. Low-temperature magnetoresistance is positive and anisotropic. The results are interpreted in the framework of the three-dimensional weak localization theory with an anisotropic diffusion constant. Dephasing scattering lengths extracted from the magnetoresistance data are well described by a theory of the electron-electron interaction in disordered metals.

Negative Magnetoresistance and Magnetic Susceptibility of Boronated Graphite

Boronated graphite specimens were prepared from a grafoil heat-treated at 3000°C for 30 min. The transport properties, such as the electrical resistivity, Hall coefficient and transverse magnetoresistance, and the total magnetic susceptibility were measured for the pristine and boronated specimens. For the specimen with high boron concentration, a negative transverse magnetoresistance at liquid nitrogen temperature and weakly temperature-dependent resistivity were observed. Assuming that the negative magnetoresistance is due to a three-dimensional weak localization, a calculation was carried out for the temperature dependence of the resistivity and transverse magnetoresistance at low temperatures in terms of Slonczewski-Weiss-McClure band model and a weak localization theory obtained by extending Kawabata's theory. The experimental finding agreed well with that the calculation predicted.

Metallic conductivity in bundles ofFeCl3-intercalated multiwall carbon nanotubes

We propose a model for the low-temperature conductivity of intercalated multiwall carbon nanotube bundles in terms of three-dimensional weak localization, with a weakly temperature-dependent inelastic scattering process, and interaction effect. At a crossover temperature ${T}^{*},$ weak localization conditions collapse and the intrinsic conduction process is observed at $T>{T}^{*}.$

Weak and Strong Localization in Three-Dimensional Granular Bismuth Films

For various kinds of thick granular Bi films, conductivity and magnetoresistance (MR) have been measured at low temperatures down to 0.05 K in magnetic fields up to 84 kOe. Corresponding to the degree of disorder in a sample, systematic results have been obtained at low temperatures. For samples of low resistivity, conductivity with T 1/2 dependence and anomalous positive MR appear. These are well explained by the three-dimensional weak localization theory taking account of spin-orbit interaction. The inelastic scattering time shows T -3/2 dependence. For samples of high resistivity, large change of conductivity with log T dependence and large positive MR with log H dependence are observed. For the sample of the highest resistivity, the conductivity changes more rapidly than log T . The MR is positive and rather large. This saturates and slightly decreases in high magnetic fields at very low temperatures.

Localization and electron-interaction effects in metallic glasses.

Magnetoresistance measurements have been made on amorphous Lu/sub 75/Pd/sub 25/ and Lu/sub 75/Ni/sub 25/ alloys. In the absence of contributions from spin-splitting interaction (because of the high spin-orbit scattering rate 1/tau/sub so/approx. =10/sup 14/ s/sup -1/) and superconducting fluctuations, direct comparison of experimental data with three-dimensional weak localization theory can be made. Our results follow the trend predicted by theory, but are about 20% larger. Interaction effects with a negative screening parameter can explain both the discrepancy and the order of magnitude of resistivity rho(T). We obtain the inelastic scattering time tau/sub i/(T)approx. =2 x 10/sup -10/T/sup -2/ s which can be attributed to electron-phonon processes in disordered metals, according to the theory of Bergmann and Takayama. Prior results obtained for amorphous Zr/sub 40/Cu/sub 60/ are discussed only qualitatively as this alloy does exhibit superconducting fluctuations above 0.5 K.