Hanbury Brown and Twiss Correlations of Anderson Localized Waves

When light waves propagate through disordered photonic lattices, they can eventually become localized due to multiple scattering effects. Here we show experimentally that while the evolution and localization of the photon density distribution is similar in the two cases of diagonal and off-diagonal disorder, the density-density correlation carries a distinct signature of the type of disorder. We show that these differences reflect a symmetry in the spectrum and eigenmodes that exists in off-diagonally disordered lattices but is absent in lattices with diagonal disorder.Comment: 4 pages, 3 figures, comments welcom

Probing Spin-Polarized Currents in the Quantum Hall Regime

An experiment to probe spin-polarized currents in the quantum Hall regime is suggested that takes advantage of the large Zeeman-splitting in the paramagnetic diluted magnetic semiconductor zinc manganese selenide (Zn$_{1-x}$Mn$_x$Se). In the proposed experiment spin-polarized electrons are injected by ZnMnSe-contacts into a gallium arsenide (GaAs) two-dimensional electron gas (2DEG) arranged in a Hall bar geometry. We calculated the resulting Hall resistance for this experimental setup within the framework of the Landauer-B\"uttiker formalism. These calculations predict for 100% spininjection through the ZnMnSe-contacts a Hall resistance twice as high as in the case of no spin-polarized injection of charge carriers into a 2DEG for filling factor $\nu=2$. We also investigated the influence of the equilibration of the spin-polarized electrons within the 2DEG on the Hall resistance. In addition, in our model we expect no coupling between the contact and the 2DEG for odd filling factors of the 2DEG for 100% spininjection, because of the opposite sign of the g-factors of ZnMnSe and GaAs.Comment: 7 pages, 5 figure

Separately contacted edge states: A new spectroscopic tool for the investigation of the quantum Hall effect

Using an innovative combination of a quasi-Corbino sample geometry and the cross-gate technique, we have developed a method that enables us to separately contact single edge channels in the quantum Hall regime and investigate equilibration among them. Performing 4-point resistance measurements, we directly obtain information on the energetic and geometric structure of the edge region and the equilibration-length for current transport across the Landau- as well as the spin-gap. Based on an almost free choice in the number of participating edge channels and their interaction-length a systematic investigation of the parameter-space becomes possible.Comment: 8 pages, 7 figure

Dynamic Nuclear Polarization in a Quantum Hall Corbino Disk

Electrical polarization of nuclear spins is studied in a Corbino disk under a breakdown regime of the quantum Hall effect (QHE). Since the edge channels are completely absent in the Corbino disk, we conclude that the electric current flowing in the bulk channel of a quantum Hall conductor is relevant to dynamic nuclear polarization (DNP). A pump and probe measurement demonstrates that DNP emerges near the critical voltage of the QHE breakdown. The agreement of the onset voltage of DNP with that of the QHE breakdown indicates that the underlying origin of DNP is closely related to that of the QHE breakdown.Comment: 3 pages, 4 figure

Spatially resolved spectroscopy of Coma cluster early-type galaxies - II:the minor axis dataset

We present minor axis, off set major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H-3 and H-4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hbeta line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations

The Halpha Luminosity Function of the Galaxy Cluster Abell 521 at z = 0.25

We present an optical multicolor-imaging study of the galaxy cluster Abell 521 at $z = 0.25$, using Suprime-Cam on the Subaru Telescope, covering an area of $32 \times 20$ arcmin$^2$ ($9.4 \times 5.8 h_{50}^{-2}$ Mpc$^2$ at $z = 0.25$). Our imaging data taken with both a narrow-band filter, $NB816$ ($\lambda_0 = 8150$\AA and $\Delta \lambda = 120$\AA), and broad-band filters, $B,V,R_{\rm C}, i^\prime$, and $z^\prime$ allow us to find 165 H$\alpha$ emitters. We obtain the H$\alpha$ luminosity function (LF) for the cluster galaxies within 2 Mpc; the Schechter parameters are $\alpha = -0.75 \pm 0.23$, $\phi^\star = 10^{-0.25 \pm 0.20}$ Mpc$^{-3}$, and $L^\star = 10^{42.03 \pm 0.17}$ erg s$^{-1}$. Although the faint end slope, $\alpha$, is consistent with that of the local cluster H$\alpha$ LFs, the characteristic luminosity, $L^\star$, is about 6 times (or $\approx 2$ mag) brighter. This strong evolution implies that Abell 521 contains more active star-forming galaxies than the local clusters, being consistent with the observed Butcher-Oemler effect. However, the bright $L^\star$ of Abell 521 may be, at least in part, due to the dynamical condition of this cluster.Comment: 21 pages, 7 figures, ApJ, Part 1, in pres

Thermohydrodynamics in Quantum Hall Systems

A theory of thermohydrodynamics in two-dimensional electron systems in quantizing magnetic fields is developed including a nonlinear transport regime. Spatio-temporal variations of the electron temperature and the chemical potential in the local equilibrium are described by the equations of conservation with the number and thermal-energy flux densities. A model of these flux densities due to hopping and drift processes is introduced for a random potential varying slowly compared to both the magnetic length and the phase coherence length. The flux measured in the standard transport experiment is derived and is used to define a transport component of the flux density. The equations of conservation can be written in terms of the transport component only. As an illustration, the theory is applied to the Ettingshausen effect, in which a one-dimensional spatial variation of the electron temperature is produced perpendicular to the current.Comment: 10 pages, 1 figur

Probing the evolution of early-type galaxies using multi-colour number counts and redshift distributions

We investigate pure luminosity evolution models for early-type (elliptical and S0) galaxies (i.e., no number density change or morphology transition), and examine whether these models are consistent with observed number counts in the B, I and K bands and redshift distributions of two samples of faint galaxies selected in the I and K bands. The models are characterized by the star formation time scale $\tau_{SF}$ and the time $t_{gw}$ when galactic wind blows in addition to several other conventional parameters. We find the single-burst model ($\tau_{SF}$=0.1 Gyr and $t_{gw}$=0.353 Gyr), which is known to reproduce the photometric properties of early-type galaxies in clusters, is inconsistent with redshift distributions of early-type galaxies in the field environment due to overpredictions of galaxies at z\gsim1.4 even with strong extinction which is at work until $t_{gw}$. In order for dust extinction to be more effective, we change $\tau_{SF}$ and $t_{gw}$ as free parameters, and find that models with \tau_{SF}\gsim0.5 Gyr and $t_{gw}>1.0$ Gyr can be made consistent with both the observed redshift distributions and number counts, if we introduce strong extinction $(E(B-V)\geq1$ as a peak value). These results suggest that early-type galaxies in the field environment do not have the same evolutionary history as described by the single-burst model.Comment: 6 pages including 4 PS figures; accepted for publication in MNRA

Strong, Ultra-narrow Peaks of Longitudinal and Hall Resistances in the Regime of Breakdown of the Quantum Hall Effect

With unusually slow and high-resolution sweeps of magnetic field, strong, ultra-narrow (width down to $100 {\rm \mu T}$) resistance peaks are observed in the regime of breakdown of the quantum Hall effect. The peaks are dependent on the directions and even the history of magnetic field sweeps, indicating the involvement of a very slow physical process. Such a process and the sharp peaks are, however, not predicted by existing theories. We also find a clear connection between the resistance peaks and nuclear spin polarization.Comment: 5 pages with 3 figures. To appear in PR

Electrostatic effects in coupled quantum dot-point contact-single electron transistor devices

We study the operation of a system where quantum dot (QD) and point contact (PC) defined in a two-dimensional electron gas of a high-mobility GaAs/AlGaAs heterostructure are capacitively coupled to each other and to metallic single electron transistor (SET). The charge state of the quantum dot can be probed by the point contact or single electron transistor. These can be used for sensitive detection of terahertz radiation. In this work, we explore an electrostatic model of the system. From the model, we determine the sensitivity of the point contact and the single electron transistor to the charge excitation of the quantum dot. Nearly periodic oscillations of the point contact conductance are observed in the vicinity of pinch-off voltage. They can be attributed to Coulomb blockade effect in a quasi-1D channel because of unintentional formation of small quantum dot. The latter can be a result of fluctuations in GaAs quantum well thickness