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We re-examine the charge transport induced by a weak electric field in two-dimensional quantum Hall systems in a finite, periodic box at very low temperatures. Our model covers random vector and electrostatic potentials and electron–electron interactions. The resulting linear response coefficients consist of the time-independent term σ_xy corresponding to the Hall conductance and the linearly time-dependent term γ_sy · t in the transverse and longitudinal directions s=x,y in a slow switching limit for adiabatically applying the initial electric field. The latter terms γ_sy · t are due to the acceleration of the electrons by the uniform electric field in the finite and isolated system, and so the time-independent term σ_yy corresponding to the diagonal conductance which generates dissipation of heat always vanishes. The well-known topological argument yields the integral and fractional quantization of the averaged Hall conductance over gauge parameters under the assumption that there exists a spectral gap above the ground state. In addition to this fact, we show that the averaged acceleration coefficients vanish under the same assumption. In the non-interacting case, the spectral gap between the neighboring Landau levels persists if the vector and the electrostatic potentials together satisfy a certain condition, and then the Hall conductance σ_xy without averaging exhibits the exact integral quantization with the vanishing acceleration coefficients in the infinite volume limit. We also estimate their finite size corrections. In the interacting case, the averaged Hall conductance for a non-integer filling of the electrons is quantized to a fraction not equal to an integer under the assumption that the potentials satisfy certain conditions in addition to the gap assumption. We also discuss the relation between the fractional quantum Hall effect and the Atiyah–Singer index theorem for non-Abelian gauge fields.

A double-stranded DNA molecule subject to a perpendicular gating electric field and a small mechanical strain exhibits a negative differential resistance (NDR) in its current–voltage (I–V) characteristics. Using an advanced two-dimensional tight-binding model including hopping integrals for the next nearest-neighbors, we implement perturbative strain- and tilted angle-dependent DNA helix conformation in conjunction with the theories of Slater–Koster and linear elasticity. The degree of NDR can be tuned by adjusting the tilt angle and mechanical strain of the DNA. This effect arises because of a surface charge distribution near the contacts due to the normal component of the electric field and structural change of the DNA molecule due to the strain. It is shown that enhancement of NDR peak current and a large peak-to-valley ratio of NDR are achieved by an increase of the tilt angle and stretching strain. Finally, a series of step-like current jumps without NDR features are exhibited in the weak DNA-lead coupling regime. This disappearance of NDR stems from the fact that reduced conduction through metal electrodes with a sufficiently small tunneling rate compensates the current drop.

We develop a partial charge-spin separation fermion-spin theory implemented by the gauge invariant dressed holon and spinon. In this novel approach, the physical electron is decoupled as the gauge invariant dressed holon and spinon, with the dressed holon behaviors like a spinful fermion, and represents the charge degree of freedom together with the phase part of the spin degree of freedom, while the dressed spinon is a hard-core boson, and represents the amplitude part of the spin degree of freedom, then the electron single occupancy local constraint is satisfied. Within this approach, the charge transport and spin response of the underdoped cuprates is studied. It is shown that the charge transport is mainly governed by the scattering from the dressed holons due to the dressed spinon fluctuation, while the scattering from the dressed spinons due to the dressed holon fluctuation dominates the spin response.

In this paper, a double helix model of charge transport in a DNA molecule is presented, and the transmission spectra and I–V curves of four kinds of periodic sequences DNA are obtained. The results show that the transmission characteristics of DNA are not only related to the longitudinal transport but also to the transverse transport of the molecule. The more the composition of bases, the bigger the percent of θ-direction, and the conductive ability reduces. For a different sequence with same composition, the less the number of consecutive appearance of the same base is, the lower the conductive ability.

Scanning photocurrent microscopy (SPCM) is a powerful experimental tool used to investigate spatially resolved optoelectronic properties of semiconductors and their nanostructures. Raster-scanned laser excitation generates a position-dependent photocurrent map from which carrier diffusion length, electric field distribution, doping concentration and more can be explored. In this review, we will briefly discuss the history of the technique, the theory behind locally injected carrier transport in semiconductors, the SPCM experimental setup, and recent applications of SPCM in semiconductor nanostructures. Particularly, we have shown that the minority carrier diffusion length can also be obtained by SPCM in two-dimensional semiconductors and that the local excitation can result in an internal electric field because of the difference in electron and hole mobilities.

The influence of pressure and $\beta$-radiation (1 kGy $\beta$ doses) on the charge transport mechanism, charge trapping effects in porous zeolite surfaces and breakdown voltage $(U_B)$ are discussed in atmospheric microplasmas for the first time. This is due to exposure the zeolite cathode (ZC) to $\beta$-radiation resulting in substantial decreases in the $U_B$, discharge currents and conductivity due to increase in porosity of the material. Results indicated that the enhancement of plasma light intensity and electron emission from the ZC surface with the release of trapped electrons which are captured by the defect centers following $\beta$-irradiation. The porosity of the ZC and radiation defect centers has significant influence on the charge transport of the microstructure and optical properties of the devices manufactured on its base. Thus, we confirm that the ${\mathrm{\text{ZC}}}_{\mathrm{\text{ir}}}$ is a suitable cathode material for plasma light source, field emission displays, energy storage devices and low power gas discharge electronic devices.

In this work, we have developed the simulation tools to study the pulse shape of the p-type point contact germanium (pPCGe) detectors. Charge signal pulse has been simulated within the pPCGe detectors, based on the “Shockley–Ramo modeling” and has been compared to the experimentally measured charge signal pulse. We have also utilized the “finite difference method” technique for simulating the electric field within the pPCGe detector volume to study the drifting process of the charge carrier. The simulated charge signal pulse, based on our simulation tools, has been found compatible with the experimental results.

Successful application of the LiNbO₃-based heterostructures in the integrated electronics and optoelectronics is mostly determined by the charge transport phenomenon in the LiNbO₃ since this affects their basic parameters. Depending on the particular conditions (temperature, applied field, properties of LiNbO₃/substrate heterojunction, etc.), various conduction mechanisms occur simultaneously and primarily, they can be divided into two major groups: contact-limited and bulk-limited. Identification and study of the charge transport mechanisms allow deriving the vital physical properties such as the barrier height at LiNbO₃ film/substrate interface, charged defect concentration, traps spacing as well as type and drift mobility of the carriers in the LiNbO₃ films. In this paper, the conduction mechanisms in LiNbO₃-based heterostructures are discussed in detail and electrical parameters are derived.

This work is devoted to studying the aggregation effect on the nonlinear optical (NLO) and charge transport (CT) properties of low-symmetry phthalocyanines bearing a cyclotriphosphazene moiety, a monomer, and clamshell-type bis-phthalocyanine. FE-SEM and AFM studies revealed ordered nanoaggregation in these compounds, represented as repeating objects of regular configuration, globules (340–480 nm), which contain small aggregates inside their cavity, similar to smoothed polygons (ca. 40 nm). Such specificity is not characteristic of other functionalized phthalocyanines, which we dealt with earlier. A new spectral method for estimating the aggregation threshold based on the change in extinction with increasing concentration of solutions was also implemented, and the effect of aggregation on optical limiting was demonstrated. The behavior of isomers and rotamers of bis-phthalocyanine in the presence of electric fields of various strengths was investigated with the DFT calculations, and that partially corresponds to the impact of laser radiation on molecules. It was shown that the unusual behavior of the trans-isomer in FF-DFT calculations is the reason for the worsening of the NLO and CT characteristics of bis-phthalocyanine, in which the macrocycles are strapped through a phosphazene spacer. An advanced method of multiparametric analysis has been implemented to evaluate the NLO and CT properties of the dyes in general.

In this research work we have modeled, simulated and compared the electronic charge transport for Metal-Semiconductor-Metal interfaces of Graphene Nano Ribbons (GNR) with different geometries using First-Principle calculations and Non-Equilibrium Green's Function (NEGF) method. We modeled junctions of Armchair GNR strip sandwiched between two Zigzag strips with (Z-A-Z) and Zigzag GNR strip sandwiched between two Armchair strips with (A-Z-A) using semi-empirical Extended Huckle Theory (EHT) within the framework of Non-Equilibrium Green Function (NEGF). I-V characteristics of the interfaces were visualized for various transport parameters. The distinct changes in conductance and I-V curves reported as the Width across layers, Channel length (Central part) was varied at different bias voltages from -1V to 1 V with steps of 0.25 V. From the simulated results we observed that the conductance through A-Z-A graphene junction is in the range of 10^-13 Siemens whereas the conductance through Z-A-Z graphene junction is in the range of 10^-5 Siemens. These suggested conductance controlled mechanisms for the charge transport in the graphene interfaces with different geometries is important for the design of graphene based nano scale electronic devices like Graphene FETs, Sensors.

A simple first principle model was developed based on extended Hückel-type orbital calculation, Marcus electron transport theory and two-dimensional-electron-gas model for the treatment of charge transport in conjugated polymers. Though simple and easy to compute, the effect of the applied electric-field is factored in. Based on this, a complete one-dimensional device model with a single layer of conjugated polymer sandwiched between two electrodes was developed with poly(3-hexylthiophene) (P3HT) as a case study. Simulated J-V curves show that π-π charge transport is much more pronounced than intra-chain transport, hence agree with previous findings. Using the same framework, we also calculated the absorption spectra of P3HT by considering the electronic energy barrier for electronic transitions that would satisfy Franck–Condon principle. Absorption spectra closely harmonize to experimental UV-Vis result. The model also reveals intra-chain electronic transitions to be the dominant absorption mechanism. All parameters of the model are obtained from either ab-initio Density Functional Theory (DFT) or Molecular Dynamics (MD) calculations, so that this model is capable of predicting charge transport and light absorption properties of new conjugated polymers without introducing fit parameters.