Negative differential thermal resistance in a double-chain system

Using nonequilibrium molecular dynamics simulations, we study the phenomenon of negative differential thermal resistance (NDTR) in a double-chain system. We investigate the dependence of NDTR on the external potential, inter- and intra-chain interaction and the system size. It is reported that the NDTR can occur in a small double-chain system with weak external potential and weak inter- and intra-chain interaction. We also present the influence of the external potential, inter- and intra-chain interaction and the system size on the heat current of the system through the phonon spectral analysis.     

Negative differential resistance in amorphous germanium

Results of a study of static current-voltage curves of amorphous germanium diodes with gap-type electrode construction are presented. It is shown that with increase in the interelectrode distance there occurs a transition from a switching regime with irreversible memory to a stable negative differential resistance regime. The diode current-voltage curves and data obtained by studying potential distribution over specimen length are explained with a model of space charge-limited currents.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 103–107, March, 1980.     

Negative differential resistance in nanotube devices

Carbon nanotube junctions are predicted to exhibit negative differential resistance, with very high peak-to-valley current ratios even at room temperature. We treat both nanotube p-n junctions and undoped metal-nanotube-metal junctions, calculating quantum transport through the self-consistent potential within a tight-binding approximation. The undoped junctions in particular may be suitable for device integration.     

Interface thermal resistance between dissimilar anharmonic lattices

We study interface thermal resistance (ITR) in a system consisting of two dissimilar anharmonic lattices exemplified by the Fermi-Pasta-Ulam and Frenkel-Kontorova models. It is found that the ITR is asymmetric; namely, it depends on how the temperature gradient is applied. The dependence of the ITR on the coupling constant, temperature, temperature difference, and system size is studied. Possible applications in nanoscale heat management and control are discussed.     

Negative differential resistance in ZnO coated peptide nanotube

We investigate the room temperature electronic transport properties of a zinc oxide (ZnO) coated peptide nanotube contacted with Au electrodes. Current–voltage (I–V) characteristics show asymmetric negative differential resistance (NDR) behavior along with current rectification. The NDR phenomenon is observed in both negative and positive voltage sweep scans, and found to be dependent on the scan rate and humidity. Our results suggest that the NDR is due to protonic conduction arising from water molecule redox reaction on the surface of ZnO coated peptide nanotubes rather than the conventional resonant tunneling mechanism.     

An analytical study of rotor dynamics coupled with thermal effect for a continuous rotor shaft

This paper presents an analytical analysis of a continuous rotor shaft subjected to universal temperature gradients. To this end, an analytical model is derived to investigate the generic thermal vibrations of rotor structures. The analytical solutions are obtained in a rotating frame and include parameters related with both the thermal environment and the rotor dynamic structures. This provides an insight into the mechanisms for the rotor thermal vibration. Furthermore, numerical results based on the analytical solutions are given. An index denoting the temperature gradients is proposed for the occasions with nonlinear cross-sectional temperature distributions. Finally, the factors influencing the thermal vibrations are analyzed. The results show that the thermal vibration is affected by many factors including the shaft size, rotational speeds, heating locations, critical speed, etc. Moreover, it is investigated how the convection coefficient and the heat conductivity influence the thermal vibrations in order to provide an insight into the management of thermal vibrations from the perspective of thermal aspects.     

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

By using first-principles calculations and nonequilibrium Green’s function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.     

Negative differential resistance in a carbon nanotube-based molecular junction

By applying non-equilibrium Green's function formalism combined with first-principles density functional theory, we have investigated the electronic transport properties of a carbon nanotube-based molecular junction with different terminations (H-, C- and N-). The results show that the different terminations at the carbon nanotube ends strongly affect the transport properties of the junction. The current through the N-terminated carbon nanotube junction is significant larger than that through the H- and C-terminated junctions at low biases. Moreover, negative differential resistance behaviors can be observed in the N-terminated carbon nanotube junction, whereas not in the other two cases.     

Negative differential resistance in transport through organic molecules on silicon

Recent scanning tunneling microscopy studies of individual organic molecules on Si(001) reported negative differential resistance (NDR) above a critical applied field, observations explained by a resonant tunneling model proposed prior to the experiments. Here we use both density functional theory and a many-electron GW self-energy approach to quantitatively assess the viability of this mechanism in hybrid junctions with organic molecules on Si. For cyclopentene on p-type Si(001), the frontier energy levels are calculated to be independent of applied electric fields, ruling out the proposed mechanism for NDR. Guidelines for achieving NDR are developed and illustrated with two related molecules, aminocyclopentene and pyrroline.     

Extremal coupled map lattices

Multifractal critical phenomena with infinite-temperature critical point and with complex coexistence of the infinite and finite temperature critical points are considered and it is shown that strange attractors generated by cascades of period-doubling bifurcations (Feigenbaum scenario) as well as fields of velocity differences in fluid turbulence belong to the former subclass of the multifractal critical phenomena, while the real traffic processes and real currency exchange processes belong to the last (complex) subclass of the multifractal critical phenomena. Data obtained by different authors are used for this purpose. Received 5 February 1999     

Bifurcations in globally coupled map lattices

The dynamics of globally coupled map lattices can be described in terms of a nonlinear Frobenius-Perron equation in the limit of large system size. This approach allows for an analytical computation of stationary states and their stability. The bifurcation behavior of coupled tent maps near the chaotic band merging point is presented. Furthermore, the time-independent states of coupled logistic equations are analyzed. The bifurcation diagram of the uncoupled map carries over to the map lattice. The analytical results are supplemented with numerical simulations     

Self-organized memories in coupled map lattices

Spatially extended dynamical systems subjected to a periodic external input are able to store short-term memories as a result of self-organization. This phenomenon has been used to interpret sliding charge density wave experiments, and has been found in lattices of coupled maps and oscillators. In this paper, we aim to describe the influence of a stochastic perturbation in the self-organized memories in a lattice of coupled linear and weakly nonlinear maps. We consider the case in which the coupling between maps depends on the lattice distance as a power law.     

Ising-type transitions in coupled map lattices

We study, by means of computer simulations, some models of coupled map lattices (CML) with symmetry, subject to diffusive nearest neighbor coupling, with the purpose of providing, a better understanding of the occurrence of Isingtype transitions of the type found by Miller and Huse. We argue, on the basis of numerical evidence, that such transitions are connected to the appearance of a minimum in the Lyapunov dimension of the system as a function of the coupling parameter. Two-dimensional CMLs similar to the one in Miller and Huse, but with no minimum in the Lyapunov dimension plot, have no Ising transition. The condition seems to be necessary, though by no means sufficient. We also argue, relying on the analysis of Bunimovich and Sinai, that coupled map lattices should behave differently, with respect to dimension, than Ising models.Dedicated to Yakov Grigorievich Sinai on his 60th birthday.     

Spatio-temporal intermittency in coupled map lattices

The transition to turbulence in a one-dimensional array of maps coupled by diffusion is shown to display critical properties resembling those of directed percolation. The analogy is supported by the reconstruction of a probabilistic cellular automation with closely similar statistical properties. Numerical results suggest however that spatio-temporal intermittency does not belong to the same universality class as directed percolation.     

Negative differential resistance in thin-film electroluminescent emitters based on zinc sulfide

S-and N-type negative differential resistance (NDR) has been observed in thin-film electroluminescent emitters based on zinc sulfide doped with manganese, and conditions for its emergence have been identified. It has been found that when a negative half-wave of voltage is applied to the nontransparent top electrode, an S-type NDR with a region of decreasing current is observed, and when it is applied to the transparent bottom electrode, the NDR will be N-type. The emergence of NDR is due to space charges which form in the near-cathode and near-anode layers of the phosphor.     

Negative differential resistance in polymer molecular devices modulated with molecular length

We study the electronic transport properties of polymer molecular devices by applying first-principles method. The results show that the electronic transport properties depend on molecular length. Negative differential resistance can be observed and can be modulated with molecular length.     

Overview of coupled map lattices

Studies in coupled map lattices are briefly surveyed in connection with the papers in the present focus issue.     

Entropy of coupled map lattices

The entropy of coupled map lattices with respect to the group of space-time translations is considered. We use the notion of generalized Lyapunov spectra to prove the analogue of the Ruelle inequality and the Pesin formula.     

Negative differential resistance and quantum oscillations in FeSb_2 with embedded antimony

We present a systematical study on single crystalline FeSb2 using electrical transport and magnetic torque measurements at low temperatures. Nonlinear magnetic field dependence of Hall resistivity demonstrates a multi-carrier transport instinct of the electronic transport. Current-controlled negative differential resistance(CC-NDR) observed in currentvoltage characteristics below ～ 7 K is closely associated with the intrinsic transition ～ 5 K of FeSb2, which is, however,mediated by extrinsic current-induced Joule heating effect. The antimony crystallized in a preferred orientation within the FeSb2 lattice in the high-temperature synthesis process leaves its fingerprint in the de Haas-Van Alphen(dHvA) oscillations, and results in the regular angular dependence of the oscillating frequencies. Nevertheless, possible existence of intrinsic non-trivial states cannot be completely ruled out. Our findings call for further theoretical and experimental studies to explore novel physics on flux-free grown FeSb_2 crystals.     

Kink dynamics in one-dimensional coupled map lattices

We examine the problem of the dynamics of interfaces in a one-dimensional space-time discrete dynamical system. Two different regimes are studied: the non-propagating and the propagating one. In the first case, after proving the existence of such solutions, we show how they can be described using Taylor expansions. The second situation deals with the assumption of a travelling wave to follow the kink propagation. Then a comparison with the corresponding continuous model is proposed. We find that these methods are useful in simple dynamical situations but their application to complex dynamical behaviour is not yet understood. (c) 1995 American Institute of Physics.