Experimental Study Of Transport Properties Research Articles

Experimental study of transport properties of Weyl semimetal LaAlGe thin films grown by molecular beam epitaxy

Rare earth compounds display diverse electronic, magnetic, and magnetotransport properties. Recently, these compounds of the type RAlGe (R = La, Ce, Pr) have been shown to exhibit Weyl semimetallic behavior. In this work, we have investigated the crystal structure and electronic and magnetotransport properties of the Weyl semimetal LaAlGe thin films grown by molecular beam epitaxy. The temperature dependence of longitudinal resistivity at different magnetic fields is discussed. Observations of magnetoresistances and the Hall effect at different temperatures and their evolution with magnetic fields up to 6 T are also discussed with relevant mechanisms. We have observed positive unsaturated magnetoresistances with a small quadratic contribution at low temperatures, which tend to saturate at higher fields. The Hall measurements confirm the electron-dominated semimetallic conduction with an average charge carrier density of ∼9.68 × 1021 cm−3 at room temperature.

Off-stoichiometric silver antimony telluride: An experimental study of transport properties with intrinsic and extrinsic doping

AgSbTe2 is a thermoelectric semiconductor with an intrinsically low thermal conductivity and a valence band structure that is favorable to obtaining a high thermoelectric figure of merit zT. It also has a very small energy gap Eg ∼ 7.6 ± 3 meV. As this gap is less than the thermal excitation energy at room temperature, near-intrinsic AgSbTe2 is a two carrier system having both holes (concentration p) and electrons (n). Good thermoelectric performance requires heavy p-type doping (p > > n). This can be achieved with native defects or with extrinsic doping, e.g. with transition metal element. The use of defect doping is complicated by the fact that many of the ternary Ag-Sb-Te and pseudo-binary Sb2Te3-Ag2Te phase diagrams are contradictory. This paper determines the compositional region most favorable to creating a single phase material. Through a combination of intrinsic and extrinsic doping, values of zT > 1 are achieved, though not on single-phased material. Additionally, we show that thermal conductivity is not affected by defects, further demonstrating that the low lattice thermal conductivity of I-V-VI2 materials is due to an intrinsic mechanism, insensitive to changes in defect structure.

Permeation and sorption properties of poly(ether-block-amide) membranes filled by two types of zeolites

The experimental study of transport properties of mixed matrix membranes (MMMs) based on PEBA-4033 with two types of zeolites is reported. Gas (CO 2, O 2, N 2) and vapor (benzene, toluene, methanol, water) permeation measurements were performed using the differential flow permeameter at temperature of 298.15 K and at atmospheric pressure. Gas/vapor permeation was monitored by measuring the changes of the thermal conductivity of carrier gas (H 2). Sorption experiments were performed gravimetrically. Determined values of the transport parameters (permeability, diffusion and sorption coefficients) of all studied vapors revealed expected high-order permeability of PEBA based membranes for vapors in comparison with gases whereas increasing of zeolite-filler content up to 30 wt.% in polymer matrix led to higher values of permeability and gas/gas and vapor/gas selectivity in comparison with pure polymer.

Transport Properties of the Two-Dimensional Wigner Solid on Liquid Helium in the Presence of a High-Frequency Damaging Electric Field

Experimental studies of transport properties of the two-dimensional (2D) Wigner solid (WS) over a liquid helium surface are performed in the presence of an additional (damaging) high frequency electric field. Surface electrons are in the linear transport regime with regard to the driving electric field created by a potential of a small amplitude (about 1 mV) whose frequency varies in the range 3–8 MHz. The damaging potential applied simultaneously has substantially higher amplitudes (30–300 mV) and frequency 36 MHz. The evolution of resonance spectra of the coupled phonon-ripplon system, electron resistivity, and the effective mass of surface dimples caused by an increase in the damaging electric field amplitude is observed. At a certain damaging potential of about 300 mV the major electron-ripplon resonance is shown to disappear, which is accompanied by a sharp decrease in the dimple effective mass, and electron resistivity. Experimental data are explained by a theoretical model of high-frequency WS decoupling from surface dimples caused by the breakdown of the balance of forces applied to the WS.

Resonant Andreev transmission in two-dimensional array of SNS junctions

We present an experimental study of transport properties of a large two-dimensional array of superconductor–normal-metal–superconductor (SNS) junctions comprised of the nanopatterned superconducting film, ensuring that NS interfaces of our SNS junctions are highly transparent. We find the anomalously high charge transmission at certain applied voltages commensurate with the magnitude of the gap in superconducting islands. This indicates the nonlocal nature of the charge transfer in multiply connected SNS systems. We propose the mechanism of the correlated transmission of Cooper pairs in large arrays of SNS junctions based on the combined action of the proximity effect and the simultaneous Andreev conversion processes at many NS-interfaces.

About this title

Muds and mudstones are the prime control on fluid flow in sedimentary basins and near-surface environments. As the world's commonest sediment type, they act as aquitards in sedimentary basins, restricting water flow and influencing the development of overpressure. In petroleum systems they act as source rocks for nearly all oil and much gas, determine migration directions between source and trap in most settings, and act as seals to many reservoirs. In near surface environments they not only control natural flow, but have been commonly used to restrict leakage from waste disposal sites. This volume focuses on the previously poorly described physical properties of muds and mudstones in both near-surface and deep basinal settings. Amongst its contents are reviews of the compaction, permeability, thermal conductivity and mechanical properties of mudstones, experimental studies of transport properties, and case studies of the importance of fluid flow in both hydrogeological and petroleum systems.

An experimental study of transport properties of porous rock salt

The influence of porosity on the transport properties of rock salt was investigated on a set of artificial porous rock salt samples. The porosities of the samples range from 5% to 42%. To study the influence of compaction on the pore space structure, five samples representing the investigated porosity range were used to produce thin sections for the analysis of the pore geometry. Permeabilities and electrical formation resistivity factors were measured with a saturated salt solution as pore fluid at room temperature and room pressure. Both properties show a strong correlation to porosity. Permabilities and formation resistivity factors were used in conjunction with the microscopical observations of the mean pore sizes to derive a parameter describing the influence of the constrictions of the transport paths. It is shown that the influence of increasing constrictivity on the transport properties is much stronger than that of decreasing porosity for the mechanically compacted samples.

Superconducting coupling along the c-axis of [001] twist grain-boundaries in Bi 2Sr 2CaCu 2O 8+δ bicrystals

We report experimental studies of transport properties of superconducting Bi 2Sr 2CaCu 2O 8+δ (Bi-2212) bicrystals with various degrees of high quality [001] twist grain boundaries. We find similar resistive onset temperature and field for both the grain-boundary and the constituent single crystals. Critical current across the grain boundaries is essentially independent of twist angle. These results show that the strength of superconducting coupling along the c-axis of [001] twist grain boundaries does no depend on misorientation angle.

New Results on Two Synthetic Conductors (TMTSF)2BRO4 and (BEDT-TTF)2I3

Abstract We present experimental studies of transport properties of (TMTSF)2BrO4 and (BEDTTTF)2I3. The behaviour of the TMTSF salt suggests transport via variable-range hopping among localized states. The BEDTTTF-salt exhibits thermopower which indicates almost isotropic metallic behaviour in the ab-plane.

Experimental studies of transport properties in epitaxial grown InAs0.55P0.35films deposited on semi-insulating GaAs substrate

Experimental studies of transport properties in epitaxial grown InAs_0.55P_0.35films deposited on semi-insulating GaAs substrate