Distribution functions and current-correlations in normal-metal--superconductor hetero-structures

We introduce electron-like and hole-like distribution functions, which determine the currents and the fluctuation spectra of the currents measured at a normal-conductor--superconductor hetero-structure. These distribution functions are expressed with the help of newly defined partial densities of states for hetero-structures. Voltage measurements using a weakly coupled contact on such a structure show the absence of a contact resistance to the superconducting reservoir and illustrate how the interface to the superconductor acts as an Andreev mirror. We also discuss the current-current correlations measured at two normal contacts and argue that the appearance of positive correlations is a purely mesoscopic effect, which vanishes in the limit of a large number of channels and in the average over an ensemble.Comment: 8 pages REVTeX, 1 figur

Applied policy analysis report : a solar garden for the Monterey Peninsula Unified School District: an applied analysis of solar power

Converting the delivery of electricity from traditional carbon-based to photovoltaic energy may provide financial relief to the Monterey Peninsula Unified School District. State Assembly Bill 32 and the state superintendent\u27s \u27Schools of Future\u27 vision direct school districts toward sustainable energy. Options to reduce power costs, generate revenue and to increase academic services using solar power are explored

Local non-equilibrium distribution of charge carriers in a phase-coherent conductor

We use the scattering matrix approach to derive generalized Bardeen-like formulae for the conductances between the contacts of a phase-coherent multiprobe conductor and a tunneling tip which probes its surface. These conductances are proportional to local partial densities of states, called injectivities and emissivities. The current and the current fluctuations measured at the tip are related to an effective local non-equilibrium distribution function. This distribution function contains the quantum-mechanical phase-coherence of the charge carriers in the conductor and is given as products of injectivities and the Fermi distribution functions in the electron reservoirs. The results are illustrated for measurements on ballistic conductors with barriers and for diffusive conductors.Comment: 4 pages, 2 figures, submitted to "Comptes Rendus de l'Academie des Sciences

Charge Fluctuations in the Edge States of N-S hybrid Nano-Structures

In this work we show how to calculate the equilibrium and non-equilibrium charge fluctuations in a gated normal mesoscopic conductor which is attached to one normal lead and one superconducting lead. We then consider an example where the structure is placed in a high magnetic field, such that the transport is dominated by edge states. We calculate the equilibrium and non-equilibrium charge fluctuations in the gate, for a single edge state, comparing our results to those for the same system, but with two normal leads. We then consider the specific example of a quantum point contact and calculate the charge fluctuations in the gate for more than one edge state.Comment: 4 pages with 1 figure. In published version the high magnetic field dynamics of the holes is treated incorrectly. An erratum is in preparatio

Relation Between Local Temperature Gradients and the Direction of Heat Flow in Quantum Driven Systems

We introduce thermometers to define the local temperature of an electronic system driven out-of-equilibrium by local ac fields. We discuss the behavior of the local temperature along the sample, showing that it exhibits spatial fluctuations following an oscillatory pattern. We show explicitly that the local temperature is the correct indicator for heat flow.Comment: 3 pages, 2 figure

Rigid Multidimensional Alkoxyamines: A Versatile Building Block Library

Since the discovery of the “living” free‐radical polymerization, alkoxyamines were widely used in nitroxide‐mediated polymerization (NMP). Most of the known alkoxyamines bear just one functionality with only a few exceptions bearing two or more alkoxyamine units. Herein, we present a library of novel multidimensional alkoxyamines based on commercially available, rigid, aromatic core structures. A versatile approach allows the introduction of different sidechains which have an impact on the steric hindrance and dissociation behavior of the alkoxyamines. The reaction to the alkoxyamines was optimized by implementing a mild and reliable procedure to give all target compounds in high yields. Utilization of biphenyl, p‐terphenyl, 1,3,5‐triphenylbenzene, tetraphenylethylene, and tetraphenyl‐methane results in linear, trigonal, square planar, and tetrahedral shaped alkoxyamines. These building blocks are useful initiators for multifold NMP leading to star‐shaped polymers or as a linker for the nitroxide exchange reaction (NER), to obtain dynamic frameworks with a tunable crosslinking degree and self‐healing abilities

Charge Current Density from the Scattering Matrix

A method to derive the charge current density and its quantum mechanical correlation from the scattering matrix is discussed for quantum scattering systems described by a time-dependent Hamiltonian operator. The current density and charge density are expressed with the help of functional derivatives with respect to the vector potential and the electric potential. A condition imposed by the requirement that these local quantities are gauge invariant is considered. Our formulas lead to a direct relation between the local density of states and the total current density at a given energy. To illustrate the results we consider, as an example, a chiral ladder model.Comment: 4 pages, 1 figur