Charging effects in quantum wires

We investigate the role of charging effects in a voltage-biased quantum wire. Both the finite range of the Coulomb interaction and the long-ranged nature of the Friedel oscillation imply a finite capacitance, leading to a charging energy. While observable Coulomb blockade effects are absent for a single impurity, they are crucial if islands are present. For a double barrier, we give the resonance condition, fully taking into account the charging of the island.Comment: 6 Pages RevTeX, no figures, Phys. Rev. B (in press

Influence of plasma nucleus form on radiation orientation in high-current pulse plasma diode

The factors accompanied the generation directed super-radiation in high-current pulse discharge in tin vapor are investigated. Basing on measurements of space distribution of radiation intensity and fixing of discharge evolution phases images it was shown that generation of directed super-radiation occurs in the moment of plasma jet gushes from dense plasma formations situated close to the anode, and the orientation of super-radiation is the same as the plasma jet one. It was drown a conclusion about the presence of radiation-stimulated radiation effect in multiply ionized plasma

Influence of external magnetic field on intensity and directivity of EUV radiation from high-current pulse plasma diode

This work is devoted to evaluate the influence of the additional external magnetic field on dynamics of the radiation in the extreme ultraviolet (EUV) range from multi-charged tin plasma of high-current pulse diode. Investigations have shown that the use of an additional external magnetic field has improved the stability of the plasma diode, enhanced the intensity of radiation, and changed the radiation profile.Работа посвящена оценке влияния дополнительного внешнего магнитного поля на динамику излучения в диапазоне вакуумного ультрафиолета (ВУФ) из многозарядной плазмы олова сильноточного импульсного диода. Исследования показали, что использование внешнего магнитного поля позволяет улучшить стабильность работы плазменного диода, повысить интенсивность излучения и изменять диаграмму направленности излучения.Робота присвячена оцінці впливу додаткового магнітного поля на динаміку випромінювання в діапазоні екстремального вакуумного ультрафіолету (ВУФ) з багатозарядної плазми олова сильнострумного імпульсного діодa. Дослідження показали, що використання зовнішнього магнітного поля дозволяє покращити стабільність роботи плазмового діодa, збільшити інтенсивність випромінювання та змінювати діаграму спрямованості випромінювання

On the statistical significance of the conductance quantization

Recent experiments on atomic-scale metallic contacts have shown that the quantization of the conductance appears clearly only after the average of the experimental results. Motivated by these results we have analyzed a simplified model system in which a narrow neck is randomly coupled to wide ideal leads, both in absence and presence of time reversal invariance. Based on Random Matrix Theory we study analytically the probability distribution for the conductance of such system. As the width of the leads increases the distribution for the conductance becomes sharply peaked close to an integer multiple of the quantum of conductance. Our results suggest a possible statistical origin of conductance quantization in atomic-scale metallic contacts.Comment: 4 pages, Tex and 3 figures. To be published in PR

Dynamical electron transport through a nanoelectromechanical wire in a magnetic field

We investigate dynamical transport properties of interacting electrons moving in a vibrating nanoelectromechanical wire in a magnetic field. We have built an exactly solvable model in which electric current and mechanical oscillation are treated fully quantum mechanically on an equal footing. Quantum mechanically fluctuating Aharonov-Bohm phases obtained by the electrons cause nontrivial contribution to mechanical vibration and electrical conduction of the wire. We demonstrate our theory by calculating the admittance of the wire which are influenced by the multiple interplay between the mechanical and the electrical energy scales, magnetic field strength, and the electron-electron interaction

How backscattering off a point impurity can enhance the current and make the conductance greater than e^2/h per channel

It is well known that while forward scattering has no effect on the conductance of one-dimensional systems, backscattering off a static impurity suppresses the current. We study the effect of a time-dependent point impurity on the conductance of a one-channel quantum wire. At strong repulsive interaction (Luttinger liquid parameter g<1/2), backscattering renders the linear conductance greater than its value e^2/h in the absence of the impurity. A possible experimental realization of our model is a constricted quantum wire or a constricted Hall bar at fractional filling factors nu=1/(2n+1) with a time-dependent voltage at the constriction.Comment: 7 pages, 2 figure

Quantum Monte Carlo simulation for the conductance of one-dimensional quantum spin systems

Recently, the stochastic series expansion (SSE) has been proposed as a powerful MC-method, which allows simulations at low $T$ for quantum-spin systems. We show that the SSE allows to compute the magnetic conductance for various one-dimensional spin systems without further approximations. We consider various modifications of the anisotropic Heisenberg chain. We recover the Kane-Fisher scaling for one impurity in a Luttinger-liquid and study the influence of non-interacting leads for the conductance of an interacting system.Comment: 8 pages, 9 figure

Fabry-Perot interference and spin filtering in carbon nanotubes

We study the two-terminal transport properties of a metallic single-walled carbon nanotube with good contacts to electrodes, which have recently been shown [W. Liang et al, Nature 441, 665-669 (2001)] to conduct ballistically with weak backscattering occurring mainly at the two contacts. The measured conductance, as a function of bias and gate voltages, shows an oscillating pattern of quantum interference. We show how such patterns can be understood and calculated, taking into account Luttinger liquid effects resulting from strong Coulomb interactions in the nanotube. We treat back-scattering in the contacts perturbatively and use the Keldysh formalism to treat non-equilibrium effects due to the non-zero bias voltage. Going beyond current experiments, we include the effects of possible ferromagnetic polarization of the leads to describe spin transport in carbon nanotubes. We thereby describe both incoherent spin injection and coherent resonant spin transport between the two leads. Spin currents can be produced in both ways, but only the latter allow this spin current to be controlled using an external gate. In all cases, the spin currents, charge currents, and magnetization of the nanotube exhibit components varying quasiperiodically with bias voltage, approximately as a superposition of periodic interference oscillations of spin- and charge-carrying ``quasiparticles'' in the nanotube, each with its own period. The amplitude of the higher-period signal is largest in single-mode quantum wires, and is somewhat suppressed in metallic nanotubes due to their sub-band degeneracy.Comment: 12 pages, 6 figure

Conductance renormalization and conductivity of a multi-subband Tomonaga-Luttinger model

We studied the conductance renormalization and conductivity of multi-subband Tomonaga-Luttinger models with inter-subband interactions. We found that, as in single-band systems, the conductance of a multi-subband system with an arbitrary number of subbands is not renormalized due to interaction between electrons. We derived a formula for the conductivity in multi-subband models. We applied it to a simplified case and found that inter-subband interaction enhances the conductivity, which is contrary to the intra-subband repulsive interaction, and that the conductivity is further enhanced for a larger number of subbands.Comment: 12 pages, no figures. to be published in Physical Review B as a brief repor

The conductance of interacting nano-wires

The conductance of one-dimensional nano-wires of interacting electrons connected to non-interacting leads is calculated in the linear response regime. Two different approaches are used: a many-body Green function technique and a relation to the persistent current recently proposed based on results of the non-interacting case. The conductance is evaluated using the functional renormalization group method and the density matrix renormalization group algorithm. Our results give a strong indication that the idea of obtaining the conductance from the persistent current holds for interacting systems.Comment: version accepted for publication in Phys. Rev.