Supersensitive avalanche silicon drift photodetector

Physical principles of performance and main characteristics of a novel avalanche photodetector developed on the basis of MOS(metal-oxide-silicon) technology is presented. The photodetector contains a semitransparent gate electrode and a drain contact to provide a drift of multiplicated charge carriers along the semiconductor surface. A high gain(more than 10^4) of photocurrent was achived due to the local negative feedback effect realizied on the Si-SiO_2 boundary. Special attention is paid to the possibilities of development of a supersensitive avalanche CCD (charge coupled device) for detection of individual photons in visible and ultraviolet spectral regions. Experimental results obtained with a two-element CCD prototype are discussed.Comment: 3 page

Enhanced collimated GeV monoenergetic ion acceleration from a shaped foil target irradiated by a circularly polarized laser pulse

Using multi-dimensional particle-in-cell (PIC) simulations we study ion acceleration from a foil irradiated by a circularly polarized laser pulse at 1022W/cm^2 intensity. When the foil is shaped initially in the transverse direction to match the laser intensity profile, the center part of the target can be uniformly accelerated for a longer time compared to a usual flat target. Target deformation and undesirable plasma heating are effectively suppressed. The final energy spectrum of the accelerated ion beam is improved dramatically. Collimated GeV quasi-mono-energetic ion beams carrying as much as 18% of the laser energy are observed in multi-dimensional simulations. Radiation damping effects are also checked in the simulations.Comment: 4 pages, 4 figure

On the Relation of Hard X-ray Peak Flux and Outburst Waiting Time in the Black Hole Transient GX 339-4

Aims. In this work we re-investigated the empirical relation between the hard X-ray peak flux and the outburst waiting time found previously in the black hole transient GX 339-4. We tested the relation using the observed hard X-ray peak flux of the 2007 outburst of GX 339-4, clarified issues about faint flares, and estimated the lower limit of hard X-ray peak flux for the next outburst. Methods. We included Swift/BAT data obtained in the past four years. Together with the CGRO/BATSE and RXTE/HEXTE light curves, the observations used in this work cover a period of 18 years. Results. The observation of the 2007 outburst confirms the empirical relation discovered before. This strengthens the apparent link between the mass in the accretion disk and the peak luminosity of the brightest hard state that the black hole transient can reach. We also show that faint flares with peak fluxes smaller than about 0.12 crab do not affect the empirical relation. We predict that the hard X-ray peak flux of the next outburst should be larger than 0.65 crab, which will make it at least the second brightest in the hard X-ray since 1991.Comment: 4 pages, 3 figures, accepted by A&

Modulated Entanglement Evolution Via Correlated Noises

We study entanglement dynamics in the presence of correlated environmental noises. Specifically, we investigate the quantum entanglement dynamics of two spins in the presence of correlated classical white noises, deriving Markov master equation and obtaining explicit solutions for several interesting classes of initial states including Bell states and X form density matrices. We show how entanglement can be enhanced or reduced by the correlation between the two participating noises.Comment: 9 pages, 4 figures. To be published in Quantum Information Processing, special issue on Quantum Decoherence and Entanglemen

Josephson φ\varphi-junctions based on structures with complex normal/ferromagnet bilayer

We demonstrate that Josephson devices with nontrivial phase difference $0<\varphi_g <\pi$ in the ground state can be realized in structures composed from longitudinally oriented normal metal (N) and ferromagnet (F) films in the weak link region. Oscillatory coupling across F-layer makes the first harmonic in the current-phase relation relatively small, while coupling across N-layer provides negative sign of the second harmonic. To derive quantitative criteria for a $\varphi$-junction, we have solved two-dimensional boundary-value problem in the frame of Usadel equations for overlap and ramp geometries of S-NF-S structures. Our numerical estimates show that $\varphi$-junctions can be fabricated using up-to-date technology.Comment: 14 pages, 9 figure

Fabrication of graphene nanogap with crystallographically matching edges and its electron emission properties

We demonstrate the fabrication of graphene nanogap with crystallographically matching edges on SiO2Si substrates by divulsion. The current-voltage measurement is then performed in a high-vacuum chamber for a graphene nanogap with few hundred nanometers separation. The parallel edges help to build uniform electrical field and allow us to perform electron emission study on individual graphene. It was found that current-voltage characteristics are governed by the space-charge-limited flow of current at low biases while the FN model fits the I-V curves in high voltage regime. We also examined electrostatic gating effect of the vacuum electronic device. Graphene nanogap with atomically parallel edges may open up opportunities for both fundamental and applied research of vacuum nanoelectronics.Comment: 12 pages,3 figures. to appear in AP

Deterministic creation of stationary entangled states by dissipation

We propose a practical physical system for creation of a stationary entanglement by dissipation without employing the environment engineering techniques. The system proposed is composed of two perfectly distinguishable atoms, through their significantly different transition frequencies, with only one atom addressed by an external laser field. We show that the arrangement would easily be realized in practice by trapping the atoms at the distance equal to the quarter-wavelength of a standing-wave laser field and locating one of the atoms at a node and the other at the successive antinode of the wave. The undesirable dipole-dipole interaction between the atoms, that could be large at this small distance, is adjusted to zero by a specific initial preparation of the atoms or by a specific polarization of the atomic dipole moments. Following this arrangement, we show that the dissipative relaxation can create a stationary entanglement on demand by tuning the Rabi frequency of the laser field to the difference between the atomic transition frequencies. The laser field dresses the atom and we identify that the entangled state occurs when the frequency of one of the Rabi sidebands of the driven atom tunes to frequency of the undriven atom. It is also found that this system behaves as a cascade open system where the fluorescence from the dressed atom drives the other atom with no feedback.Comment: Published versio

Experimental observation of negative differential resistance from an InAs/GaSb interface

We have observed negative differential resistance at room temperature from devices consisting of a single interface between n-type InAs and p-type GaSb. InAs and GaSb have a type II staggered band alignment; hence, the negative differential resistance arises from the same mechanism as in a p+-n+ tunnel diode. Room-temperature peak current densities of 8.2×10^4 A/cm^2 and 4.2×10^4 A/cm^2 were measured for structures with and without undoped spacer layers at the heterointerface, respectively