Absolute Negative Resistance Research Articles

Anomalous Negative Resistance Phenomena in Twisted Superconducting Nanowire Yarns.

We report unusual absolute negative resistance phenomena in twisted superconducting yarns consisting of niobium-nitride (NbN) nanowires formed on a template of aligned carbon nanotube (CNT) sheets. In the vicinity of the superconducting critical temperature and critical current, the electrical resistance with a standard four-probe configuration exhibits negative values for many wire-shaped twisted yarns. This anomalous behavior at the superconducting transition stage is analyzed using a simplified circuit model, where the charge conduction is determined by the combination between the intra- and internanofiber transports inside the yarn. The superconducting transition of intrafibrillar transport along CNT-templated NbN nanowires was distinguished from that of an interfibrillar one, where the latter exhibits the ensemble property of superconducting weak links among adjacent NbN nanowires. Furthermore, the topological similarity between the sheet of an aligned array of nanowires and the yarn of twisted nanofibrils enables the occurrence of this anomaly. This study indicates that the quantitative network-based approach is effective for the analysis of anomalous charge conduction through nanowire-based anisotropic materials.

Magnetoplasmon resonance in a two-dimensional electron system driven into a zero-resistance state

We report on a very strong, and a rather sharp, photoresistance peak originating from a dimensional magnetoplasmon resonance (MPR) in a high-mobility GaAs/AlGaAs quantum well driven by microwave radiation into a zero-resistance state (ZRS). The analysis of the MPR signal reveals a negative background, providing experimental evidence for the concept of absolute negative resistance associated with the ZRS. When the system is further subject to a dc field, the maxima of microwave-induced resistance oscillations decay away and the system reveals a state with close-to-zero differential resistance. The MPR peak, on the other hand, remains essentially unchanged, indicating robust Ohmic behavior under the MPR conditions.

Miniband quantum transport in semiconductor nanodevices under broadband illumination

A general theoretical framework for the modelling of miniband transport in semiconductor nanostructures under broadband illumination is presented. Our approach is based on the multi-subband three-dimensional Boltzmann transport equation and allows to investigate both the steady-state and the time-dependent dynamics. The model has been succesfully applied to the problem of the design and optimization of Terahertz quantum well infrared photodetectors and is now applied to a more generic superlattice system. We consider the carrier dynamics in multi-miniband superlattices under black-body illumination showing the existence of regimes in which the current in some minibands is inverted, eventually leading to absolute negative resistance.

Absolute negative resistance and multivaluedness on current-voltage characteristics of tunnel diodes

The effect of external perturbations of large amplitude in the form of a coherent signal or noise on the behavior of dynamic and static current-voltage (I–V) characteristics of tunnel diodes has been experimentally investigated. It is shown that, when an appropriate frequency is chosen, an increase in the amplitude of the external coherent signal leads to the occurrence of multivaluedness and absolute negative resistance on the I–V characteristics of tunnel diodes. The noise effect suppresses the N-type negative differential resistance on the I–V characteristics of tunnel diodes and significantly distorts these characteristics. A possible mechanism of the occurrence of absolute negative resistance is proposed.

Absolute negative resistance in a nonequilibrium two-dimensional electron system in a strong magnetic field

The effect of microwave electromagnetic radiation on the resistance of the 2D electron gas in a GaAs/AlAs heterostructure in a strong magnetic field is investigated. It is shown that, under the nonequilibrium conditions caused by microwave radiation, the aforementioned 2D system exhibits giant oscillations of its resistance with varying magnetic field. When the measuring current density is small, an increase in the microwave power leads to the appearance of an absolute negative resistance at the main minimum of these oscillations, which lies near the cyclotron resonance. The experimental data are found to be in qualitative agreement with the theory of multiphoton photoinduced impurity scattering [J. Inarrea and G. Platero, Appl. Phys. Lett. 89, 052109 (2006)].

Absolute Negative Resistance Induced by Directional Electron-Electron Scattering in a Two-Dimensional Electron Gas

A three-terminal device formed by two electrostatic barriers crossing an asymmetrically patterned two-dimensional electron gas displays an unusual potential depression at the middle contact, yielding absolute negative resistance. The device displays momentum and current transfer ratios that far exceed unity. The observed reversal of the current or potential in the middle terminal can be interpreted as the analog of Bernoulli's effect in a Fermi liquid. The results are explained by directional scattering of electrons in two dimensions.

Intersubband transitions in photon-assisted tunneling through a quantum wire

The photon-assisted coherent tunneling is treated by the equation of motion for nonequilibrium Green functions. The effects of intersubband transitions on the tunneling through a two-level quantum wire are investigated under different conditions by calculating the off-diagonal matrix elements of the electron-photon interaction in addition to diagonal matrix elements. The differences in density of states and current for diagonal and off-diagonal interaction are examined. It is found that electronic transitions due to multiphoton absorption are more or less suppressed when the off-diagonal interaction dominates, while both multi- and single-photon transitions are present when diagonal matrix elements dominate the interaction. Depending on the equilibrium position of Fermi surface in electrode leads, the tunneling current is found to display either peak or plateau structures in the $I\ensuremath{-}V$ curve. The necessary condition for the appearance of absolute negative resistance in either diagonal or off-diagonal interaction is discussed.

Carrier Accumulation in Momentum Space and Related Phenomena under Intense Microwave Fields in Semiconductors. II. Quasi-One-Dimensional Systems

When the dominant scattering mechanism is optical phonon emission, the application of appropriately intense microwave fields is expected to cause an accumulated distribution of carriers in momentum space and related peculiar phenomena, as described in a previous paper which treated usual bulk semiconductors. It is shown here that the carrier accumulation effect is more pronounced in one-dimensional systems in the direction of the microwave fields, because of the absence of transverse degrees of freedom. Computations are made for electrons in GaAs crystals confined by strong magnetic fields of 12∼24 T. The results show that peculiar dc field responses including absolute negative resistance are expected under realistic experimental conditions, e.g. in samples with more than 10 14 cm -3 charged impurity concentration.

Photon assisted transport through semiconductor quantum structures in intense terahertz electric fields

Quantum transport in resonant tunneling diodes, sequential resonant tunneling superlattices and miniband superlattices in the presence of intense terahertz electric fields is marked by new channels opened by the absorption or emission of one or more terahertz photons. In triple barrier resonant tunneling diodes, new transport channels supported by the absorption or stimulated emission of up to three terahertz photons are observed. In sequential resonant tunneling superlattices, dynamic localization is accompanied by absolute negative resistance. Transport in miniband resonances with controlled by coherent tunneling through several barriers and quantum wells, reveals multi-photon resonances with Bloch oscillation. Photon-assisted transport in these semiconductor quantum structures bears a strong analogy to quasi-particle tunneling and the AC Josephson effect in superconducting junctions and opens the arena of superconducting electronics to semiconductor systems. These experiments are made possible by the UCSB free-electron lasers that deliver kilowatts of tunable radiation from 120 GHz to 4.8 THz.

Absolute negative resistance in double-barrier heterostructures in a strong laser field.

A tunneling current through a double-barrier heterostructure is considered in a strong laser field. By absorbing or emitting photons an electron can penetrate through the barrier structure. As shown, the current may have both positive and negative signs dependent on the intensity of the field. I-V characteristics have a peak structure with the peaks located by an energy of two photons apart from each other. The negative amplitude of the current demonstrates the effect of an absolute negative resistance. The I-V characteristics are studied at different temperatures because of a hot-electron-distribution Fermi function in the strong field. The expression for the tunneling current is generalized to asymmetric barriers, and to the case when the Fermi energy is larger than the energy of one photon as well.

Inhomogeneously heated electron transport in MIS microstructures

Abstract It is demonstrated that in home-junction conducting metal-insulator-semiconductor (MIS) microstructures qualitatively new electron transport phenomena occur and involve an absolute negative resistance of hot electrons and a cold electron thermal bottleneck. These are due to the simultaneous existence of two physical factors: (i) high non-equilibrium electron state and (ii) its abrupt spatial inhomo-geneity. Taking as a basis the effects predicted, electron devices of two types (passive and active) are suggested.

Nonequilibrium distributions in superconductors

The nonequilibrium distribution functions of quasiparticles and phonons in superconductors are calculated for various cases. The conditions at which the nonequilibrium distributions exist are found. The dependences of the temperature and concentration of excitations on the pumping intensity, the sample thickness, and other parameters of the superconductor are calculated. In the current state the dependences of these quantities on the superfluid velocity and the current are investigated, and it is found that the dependenceT(v s ) has a minimum, and the current for vs>v so (1) becomes negative. It is also shown that in the nonequiibrium superconductor the state withv s * ≠ 0 andJ(v s * )=0 may exist. We have determined the nonequilibrium distribution function for a tunnel junction and investigated theV-A characteristic at some conditions for which an absolute negative resistance may exist.