A prohibition of equilibrium spin currents in multi-terminal ballistic devices

We show that in the multi-terminal ballistic devices with intrinsic spin-orbit interaction connected to normal metal contacts there are no equilibrium spin currents present at any given electron energy. Obviously, this statement holds also after the integration over all occupied states. Based on the proof of this fact, a number of scenarios involving nonequilibrium spin currents is identified and further analyzed. In particular, it is shown that an arbitrary two-terminal device cannot polarize transient current. The same is true for the output terminal of an N-terminal device when all N-1 inputs are connected in parallel.Comment: 3 pages, 1 figure; presented at the DARPA SPinS review (#Th-19), San Francisco, CA, October 25-28, 200

Direct determination of 2D Momentum Space from 2D Spatial Coherence of Light using a Modified Michelson Interferometer

Momentum space distributions of photons coming out of any light emitting materials/devices provide critical information about its underlying physical origin. Conventional methods of determining such properties impose specific instrumentational difficulties for probing samples kept within a low temperature cryostat. There were past studies to measure one dimensional (1D) coherence function which could then be used for extracting momentum space information as well as reports of measurements of just two dimensional (2D) coherence function. However, all of those are associated with additional experimental complexities. So, here we propose a simpler, modified Michelson interferometer based optical setup kept at room temperature outside the cryostat to initially measure the 2D coherence function of emitted light, which can then be used to directly estimate the 2D in-plane momentum space distribution by calculating its fast Fourier transform. We will also discuss how this experimental method can overcome instrumentational difficulties encountered in past studies.Comment: 23 pages, 6 figure

Break-down of the density-of-states description of scanning tunneling spectroscopy in supported metal clusters

Low-temperature scanning tunneling spectroscopy allows to probe the electronic properties of clusters at surfaces with unprecedented accuracy. By means of quantum transport theory, using realistic tunneling tips, we obtain conductance curves which considerably deviate from the cluster's density of states. Our study explains the remarkably small number of peaks in the conductance spectra observed in recent experiments. We demonstrate that the unambiguous characterization of the states on the supported clusters can be achieved with energy-resolved images, obtained from a theoretical analysis which mimics the experimental imaging procedure.Comment: 5 pages, 3 figure

Turbulence in Fluid and Plasma: Search for a New Paradigm

A first principle explanation of the origin of intermittency and nonlinear structure formation in the Lagrangian velocity increments of a turbulent flow is presented in the context of a scale invariant analytical formalism that is being developed recently. The copious generation of power laws and nonlinear exponents in the structure functions are shown to follow quite naturally in the present formalism.Comment: 10 pages, Latex2

Aktivitas Antimikroba Sopi terhadap Bakteri Patogen Salmonella Typhimurium dan Salmonella Enteritidis

Sopi is a traditional drink from East Nusa Tenggara, made through a fermentation process that is derived from palm trees (Borassus flabellifer L.) which also has the potential to be used as an antimicrobial agent. The purpose of this study was to identify the antimicrobial activity of Sopi against pathogenic bacteria. Identification of the antimicrobial activity conducted in two stages, testing the alcohol content and acidity from sopi; and bioassay testing using pathogenic bacteria Salmonella Typhimurium and Salmonella Enteritidis. The results showed that the Sopi has antimicrobial activity against pathogenic bacteria Salmonella Typhimurium and Salmonella Enteritidis. Results of this research may be basic research to the development of Sopi as an antimicrobial agent

Skrining Fitokimia Minuman Tradisional Moke dan Sopi sebagai Kandidat Antimikroba

Sopi and moke of East Nusa Tenggara Province are some traditional beverage made from nira or interest leads palm (Borassus flabellifer L.). Several studies have shown that sopi and moke have an antimicrobial activity. Antimicrobial activity of plants derivatives may be influenced by the content of phytochemical compounds. The purpose of this study was to determine the class of phytochemical compounds in sopi and moke. Phytochemical testing performed on seven chemical compounds, namely alkaloids, flavonoids, phenols hydroquinone, steroids, triterphenoid, tannins and saponins. The results show that sopi contains of alkaloids and moke contains of phenol hydroquinone and saponins. Antimicrobial activity of sopi and moke supposed to be caused by these three compounds and this could be a potential source of an alternative disinfectant candidate

Microscopic non-equilibrium theory of quantum well solar cells

We present a microscopic theory of bipolar quantum well structures in the photovoltaic regime, based on the non-equilibrium Green's function formalism for a multi band tight binding Hamiltonian. The quantum kinetic equations for the single particle Green's functions of electrons and holes are self-consistently coupled to Poisson's equation, including inter-carrier scattering on the Hartree level. Relaxation and broadening mechanisms are considered by the inclusion of acoustic and optical electron-phonon interaction in a self consistent Born approximation of the scattering self energies. Photogeneration of carriers is described on the same level in terms of a self energy derived from the standard dipole approximation of the electron-photon interaction. Results from a simple two band model are shown for the local density of states, spectral response, current spectrum, and current-voltage characteristics for generic single quantum well systems.Comment: 10 pages, 6 figures; corrected typos, changed caption Fig. 1, replaced Fig.

Electron Transport Through Molecules: Self-consistent and Non-self-consistent Approaches

A self-consistent method for calculating electron transport through a molecular device is proposed. It is based on density functional theory electronic structure calculations under periodic boundary conditions and implemented in the framework of the nonequilibrium Green function approach. To avoid the substantial computational cost in finding the I-V characteristic of large systems, we also develop an approximate but much more efficient non-self-consistent method. Here the change in effective potential in the device region caused by a bias is approximated by the main features of the voltage drop. As applications, the I-V curves of a carbon chain and an aluminum chain sandwiched between two aluminum electrodes are calculated -- two systems in which the voltage drops very differently. By comparing to the self-consistent results, we show that this non-self-consistent approach works well and can give quantitatively good results.Comment: 11 pages, 10 figure

Electron Transport Through Molecules: Gate Induced Polarization and Potential Shift

We analyze the effect of a gate on the conductance of molecules by separately evaluating the gate-induced polarization and the potential shift of the molecule relative to the leads. The calculations use ab initio density functional theory combined with a Green function method for electron transport. For a general view, we study several systems: (1) atomic chains of C or Al sandwiched between Al electrodes, (2) a benzene molecule between Au leads, and (3) (9,0) and (5,5) carbon nanotubes. We find that the polarization effect is small because of screening, while the effect of the potential shift is significant, providing a mechanism for single-molecule transistors.Comment: 4 pages, 4 figure