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Very recently, half-hydrogenated germanene has been achieved in an experiment. In this paper, we investigate the effects of tetracyanoquinodimethane (TCNQ) molecular adsorption and strain on the electronic properties of half-hydrogenated germanene through first-principles. As an electron-acceptor molecule, TCNQ is exploited to non-covalently functionalize the half-hydrogenated germanene. However, this physical adsorption induces a ferromagnetic semiconductor–metal transition in half-hydrogenated germanene due to charge transfer from the substrate to the TCNQ molecule. More importantly, the superstructure of half-hydrogenated germanene/TCNQ is extremely sensitive to biaxial tensile strain. Under the biaxial tensile strain of 0.25%, the ferromagnetic semiconductor–metal transition induced by molecular adsorption can surprisingly be overturned. Meanwhile, a strong p-type doping is exhibited. Remarkably, it would return from a ferromagnetic semiconductor to a metal again when the biaxial tensile strain increases to 1.5%. Our analysis based on the structural and electronic properties of half-hydrogenated germanene/TCNQ indicates that such metal–semiconductor–metal transition in half-hydrogenated germanene/TCNQ under biaxial tensile strain may originate from the strong local deformation, resulting in the energy of the valence band maximum decreasing below or increasing above the Fermi level. [ABSTRACT FROM AUTHOR]

We analyze a phase-sensitive contribution to the oscillating magnetoresistance induced by the combined driving of two microwave fields having commensurate frequencies ω1 and ω2 (m1ω1+m2ω2=0 for at least a set of nonzero integers m1 and m2), based on the balance-equation approach to magnetotransport for high-density two-dimensional electron systems. This commensurate oscillating photoresistance not only depends on the frequencies and polarizations of both microwaves, but varies drastically when changing the relative phases of two incident radiation fields. It shows up most significantly in the case of ω2/ω1=3 and may lead to a phase-controllable change of more than a factor of two in the total magnetoresistivity in the vicinity of ω1/ωc=1.5 and 2.5 (ωc is the cyclotron frequency), when both radiation fields are linearly x-direction polarized. [ABSTRACT FROM AUTHOR]

We analyze the effects of a distortion of the nuclear potential of a molecular quantum dot (QD) as well as a shift in its equilibrium position on nonequilibrium-vibration-assisted tunneling through the QD with a single level ([variant_greek_epsilon]d) coupled to the vibrational mode. For this purpose, we derive an explicit analytical expression for the Franck–Condon (FC) factor for a displaced-distorted oscillator surface of the molecule and establish rate equations in the joint electron-phonon representation to examine the current-voltage characteristics and zero-frequency shot noise and skewness as well. Our numerical analysis shows that the distortion has two important effects. The first one is that it breaks the symmetry between the excitation spectra of the charge states, leading to asymmetric tunneling properties with respect to [variant_greek_epsilon]d>0 and [variant_greek_epsilon]d<0. Second, distortion (frequency change in the oscillator) significantly changes the voltage-activated cascaded transition mechanism and consequently gives rise to a different nonequilibrium vibrational distribution from that of the case without distortion. Taken in conjunction with strongly modified FC factors due to distortion, this results in some new transport features: the appearance of strong negative differential conductance even for a single-level QD with symmetric tunnel couplings, a giant Fano factor even for a molecule with an extremely weak electron-phonon interaction, and enhanced skewness that can have a large negative value under certain conditions. [ABSTRACT FROM AUTHOR]

We present a kinetic equation approach to investigate dc transport properties of graphene in the diffusive regime considering long-range electron-impurity scattering. In our study, the effects of interband correlation (or polarization) on conductivity are taken into account. We find that the conductivity contains not only the usual term inversely proportional to impurity density Ni but also an anomalous term that is linear in Ni. This leads to a minimum in the density dependence of conductivity when the electron density Ne is equal to a finite critical value Nc. The effects of various scattering potentials on the conductivity minimum are also analyzed. Using typical experimental parameters, we find that for random-phase-approximation–screened electron-impurity scattering, the minimum conductivity is about 4.42e2/h when Ne≈0.11Ni, and the conductivity varies almost linearly with the electron density for Ne>Ni. [ABSTRACT FROM AUTHOR]

We examine the shot noise spectrum properties of coherent resonant tunneling in coupled quantum dots (CQDs) in both series and parallel arrangements by means of quantum rate equations and MacDonald’s formula. Our results show that for a series-CQD with a relatively high dot-dot hopping Ω and Ω/Γ>=1 (Γ denotes the dot-lead tunnel-coupling strength), the noise spectrum exhibits a dip at the Rabi frequency 2Ω in the case of noninteracting electrons, but the dip is supplanted by a peak in the case of strong Coulomb repulsion; furthermore, it becomes a dip again for a completely symmetric parallel-CQD by tuning the enclosed magnetic flux. [ABSTRACT FROM AUTHOR]

Reports on a study which analyzed the scattering for the intra- and intersubband transitions of electrons in a GaAs/AlAs quantum well with a central AlAs thin layer assisted by the emission and absorption of optical phonon modes. Application of transversal electric field through the structure; Frohlich interaction and electron mobility; Antisymmetric interface phonon modes.

Presents a study which developed a non-Boltzmann theory of a steady-state transport for two-dimensional systems in a strong electric field which includes a force- and an energy-balance equation. Method of the study; Results and discussion; Conclusion.

Proposes balance equations for high-field electron transport in nonparabolic multiband semiconductors. Relation between electron energy and lattice wave vector; Description of a balance equation for multiband systems; Findings of the study.

Deals with a study which investigated Bragg scattering and effective force-balance equations in superlattice miniband transport. Background to the study; Background on the Büttiker-Thomas momentum balance equation; Details on the acceleration and energy balance equations.

Investigates the linear and nonlinear miniband electron transport through a laterally confined superlattice using the balance-equation theory. Acceleration and energy-balance equations; Calculation of the linear and nonlinear properties of GaAs/AlAs superlattices; Linear mobilities.

Presents a study which examined linear and nonlinear characteristics of superconductor superlattice perpendicular conduction. Linear mobilities from the balance-equation theory; Comparisons between theories and experiments; Conclusions.