Cyclotron spin-wave in the 2D electron system

The cyclotron spin-wave mode of a two-dimensional electron system have been investigated by inelastic light scattering. It is observed at small electron filling factors, (v～0.1, when the electron system is spin-depolarized. As long as the electron system becomes fully spin-polarized (v>0.2), the cyclotron spin-wave disappears from the inelastic light scattering spectra. It reenters at electron filling factors v>1. Over the range of electron filling factors of 1<v<2, the cyclotron spin-wave energy is insensitive to both the experimentally accessible in-plane momenta and the electron concentration, whereas its inelastic light scattering efficiency is strongly influenced by the spin polarization of the electron system.     

Recognizing heterogeneous distribution of platinum group elements (PGE) in geological materials by means of the Re–Os isotope system

The identification of uncertainties caused by sample inhomogeneity, as distinct from those caused by sample preparation and measurement, is a challenging task. Use of chemometric methods to separate and estimate these contributions to the combined standard uncertainty of a measurement (u _c ) of an analytical result requires complex experiments. The difficulty of platinum group element measurement makes this task even more complex. But unless it can be demonstrated that sample inhomogeneity is the major contributor to the high variability of an analytical result one should be careful not to mistakenly attribute this to a nugget effect. In this contribution we are able to demonstrate in two special cases that irreproducible results (up to 90% RSD) for analysis of Os and Re in the pg g^–1 to ng g^–1 range are truly caused by a nugget effect and not by inadequacies of the analytical method.     

The wrong kind of gravity

The KPZ formula [V.G. Knizhnik, A.M. Polyakov, and A.B. Zamolodchikov, Mod. Phys. Lett. A 3 (1988) 819] shows that coupling central charge c≤1 spin models to 2D quantum gravity dresses the conformal weights to get new critical exponents, where the relation between the original and dressed weights depends only on c. At the discrete level the coupling to 2D gravity is effected by putting the spin models on annealed ensembles of Φ³ planar random graphs or their dual triangulations, where the connectivity fluctuates on the same time-scale as the spins.Since the sole determining factor in the dressing is the central charge, one could contemplate putting a spin model on a quenched ensemble of 2D gravity graphs with the “wrong” c value. We might then expect to see the critical exponents appropriate to the c value used in generating the graphs. In such cases the KPZ formula could be interpreted as giving a continuous line of critical exponents which depend on this central charge. We note that rational exponents other than the KPZ values can be generated using this procedure for the Ising, tricritical Ising and 3-state Potts models.     

Quantum dots fabricated by twofold cleaved edge overgrowth

Cleaved edge overgrowth (CEO) has proven to be a powerful technique for the fabrication of atomic scale T-shaped quantum wires (QWRs) which form at the intersection of two quantum wells (QWs). Here we report on the first experimental demonstration of quantum dots (QDs) which result when three QWs intersect each other at right angles. Optical emission from zero-dimensional (0D) states in these QDs which were fabricated by a twofold CEO technique is clearly identified by means of micro-photoluminescence ( PL) and PL excitation ( PLE) spectroscopy. In contrast to the inhomogeneously broadened QW and QWR signals originating from the complex sample structure, the QD response, which is characterised by sharp lines (FWHM 70 eV), is strongly spatially localised at a position where the QWs meet.     

Limits of detection in multivariate calibration

Summary Multivariate calibration and prediction is applied to signal data measured for selected multicomponent systems using inductively coupled plasma—optical emission spectrometry (ICP-OES). A multivariate definition of the limit of detection is derived from the error propagation theory. No limiting assumptions of constant signal errors are made for derivation. The definition is successfully applied to estimate realistic limits of detection for the investigated systems. Contributions corresponding to the calibration error were included for calculation. For efficient application realistic error models are introduced to estimate the required errors of the signals without replicate measurements.     

Normalized Solutions of Schrödinger Equations with Potentially Bounded Measures

Given a potentially bounded signed measure on a Brelot space (X,) with Green function G, it is well known that -harmonic functions (i.e., in the classical case, finely continuous versions of solutions to u–u=0) may be very discontinuous. In this paper it is shown that under very general assumptions on G (satisfied for large classes of elliptic second-order linear differential operators) normalized perturbation, however, leads to a Brelot space (X, ) admitting a Green function T (G) which is locally (or even globally) comparable with G and has all properties required of G before. In particular, iterated perturbation is possible. Moreover, intrinsic Hölder continuity of quotients of harmonic functions with respect to the local quasimetric :=(G ^–1+^* G ^–1)/2 yields -Hölder continuity for quotients of -harmonic functions as well.     

Single-electron-phonon interaction in a suspended quantum dot phonon cavity

An electron-phonon cavity consisting of a quantum dot embedded in a freestanding GaAs/AlGaAs membrane is characterized using Coulomb blockade measurements at low temperatures. We find a complete suppression of single electron tunneling around zero bias leading to the formation of an energy gap in the transport spectrum. The observed effect is induced by the excitation of a localized phonon mode confined in the cavity. This phonon blockade of transport is lifted at discrete magnetic fields where higher electronic states with nonzero angular momentum are brought into resonance with the phonon energy.