Magnetoconductance of carbon nanotube p-n junctions

The magnetoconductance of p-n junctions formed in clean single wall carbon nanotubes is studied in the noninteracting electron approximation and perturbatively in electron-electron interaction, in the geometry where a magnetic field is along the tube axis. For long junctions the low temperature magnetoconductance is anomalously large: the relative change in the conductance becomes of order unity even when the flux through the tube is much smaller than the flux quantum. The magnetoconductance is negative for metallic tubes. For semiconducting and small gap tubes the magnetoconductance is nonmonotonic; positive at small and negative at large fields.Comment: 5 pages, 2 figure

Absorption of heat into a superconductor-normal metal-superconductor junction from a fluctuating environment

We study a diffusive superconductor-normal metal-superconductor junction in an environment with intrinsic incoherent fluctuations which couple to the junction through an electromagnetic field. When the temperature of the junction differs from that of the environment, this coupling leads to an energy transfer between the two systems, taking the junction out of equilibrium. We describe this effect in the linear response regime and show that the change in the supercurrent induced by this coupling leads to qualitative changes in the current-phase relation and for a certain range of parameters, an increase in the critical current of the junction. Besides normal metals, similar effects can be expected also in other conducting weak links.Comment: 5 pages, 4 figures - supplementary information included: 3 pages, 1 figure; minor modifications to the text and Fig. 2, added Ref. 1

A quantum hydrodynamics approach to the formation of new types of waves in polarized two-dimension systems of charged and neutral particles

In this paper we explicate a method of quantum hydrodynamics (QHD) for the study of the quantum evolution of a system of polarized particles. Though we focused primarily on the two-dimension physical systems, the method is valid for three-dimension and one-dimension systems too. The presented method is based upon the Schr\"{o}dinger equation. Fundamental QHD equations for charged and neutral particles were derived from the many-particle microscopic Schr\"{o}dinger equation. The fact that particles possess the electric dipole moment (EDM) was taken into account. The explicated QHD approach was used to study dispersion characteristics of various physical systems. We analyzed dispersion of waves in a two-dimension (2D) ion and hole gas placed into an external electric field which is orthogonal to the gas plane. Elementary excitations in a system of neutral polarized particles were studied for 1D, 2D and 3D cases. The polarization dynamics in systems of both neutral and charged particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. We also analyzed wave dispersion in 2D exciton systems, in 2D electron-ion plasma and 2D electron-hole plasma. Generation of waves in 3D system neutral particles with EDM by means of the beam of electrons and neutral polarized particles is investigated.Comment: 15 pages, 7 figure

Superconductor-semiconductor magnetic microswitch

A hybrid superconductor--two-dimensional electron gas microdevice is presented. Its working principle is based on the suppression of Andreev reflection at the superconductor-semiconductor interface caused by a magnetic barrier generated by a ferromagnetic strip placed on top of the structure. Device switching is predicted with fields up to some mT and working frequencies of several GHz, making it promising for applications ranging from microswitches and storage cells to magnetic field discriminators.Comment: 4 pages, 3 figures, minor changes to tex

Re-entrant localization of single particle transport in disordered Andreev wires

We study effects of disorder on the low energy single particle transport in a normal wire surrounded by a superconductor. We show that the heat conductance includes the Andreev diffusion decreasing with increase in the mean free path $\ell$ and the diffusive drift produced by a small particle-hole asymmetry, which increases with increasing $\ell$. The conductance thus has a minimum as a function of $\ell$ which leads to a peculiar re-entrant localization as a function of the mean free path.Comment: 4 pages, 2 figure

Novel relativistic plasma excitations in a gated two-dimensional electron system

The microwave response of a two-dimensional electron system (2DES) covered by a conducting top gate is investigated in the relativistic regime for which the 2D conductivity $\sigma_{2 \rm{D}} > c/2\pi$. Weakly damped plasma waves are excited in the gated region of the 2DES. The frequency and amplitude of the resulting plasma excitations show a very unusual dependence on the magnetic field, conductivity, gate geometry and separation from the 2DES. We show that such relativistic plasmons survive for temperatures up to 300 K, allowing for new room-temperature microwave and terahertz applications.Comment: 9 pages, 7 figure

A superfluid-droplet crystal and a free-space supersolid in a dipole-blockaded gas

A novel supersolid phase is predicted for an ensemble of Rydberg atoms in the dipole-blockade regime, interacting via a repulsive dipolar potential "softened" at short distances. Using exact numerical techniques, we study the low temperature phase diagram of this system, and observe an intriguing phase consisting of a crystal of mesoscopic superfluid droplets. At low temperature, phase coherence throughout the whole system, and the ensuing bulk superfluidity, are established through tunnelling of identical particles between neighbouring droplets.Comment: 4 pages, 4 figure

Two-photon correlations as a sign of sharp transition in quark-gluon plasma

The photon production arising due to time variation of the medium has been considered. The Hamilton formalism for photons in time-variable medium (plasma) has been developed with application to inclusive photon production. The results have been used for calculation of the photon production in the course of transition from quark-gluon phase to hadronic phase in relativistic heavy ion collisions. The relative strength of the effect as well as specific two- photon correlations have been evaluated. It has been demonstrated that the opposite side two-photon correlations are indicative of the sharp transition from the quark-gluon phase to hadrons.Comment: 23 pages, 2 figure

Frobenius-Perron Resonances for Maps with a Mixed Phase Space

Resonances of the time evolution (Frobenius-Perron) operator P for phase space densities have recently been shown to play a key role for the interrelations of classical, semiclassical and quantum dynamics. Efficient methods to determine resonances are thus in demand, in particular for Hamiltonian systems displaying a mix of chaotic and regular behavior. We present a powerful method based on truncating P to a finite matrix which not only allows to identify resonances but also the associated phase space structures. It is demonstrated to work well for a prototypical dynamical system.Comment: 5 pages, 2 figures, 2nd version as published (minor changes

Normal metal - superconductor tunnel junction as a Brownian refrigerator

Thermal noise generated by a hot resistor (resistance $R$) can, under proper conditions, catalyze heat removal from a cold normal metal (N) in contact with a superconductor (S) via a tunnel barrier. Such a NIS junction acts as Maxwell's demon, rectifying the heat flow. Upon reversal of the temperature gradient between the resistor and the junction the heat fluxes are reversed: this presents a regime which is not accessible in an ordinary voltage-biased NIS structure. We obtain analytical results for the cooling performance in an idealized high impedance environment, and perform numerical calculations for general $R$. We conclude by assessing the experimental feasibility of the proposed effect