1,485 research outputs found
Double quantum dots as a high sensitive submillimeter-wave detector
A single electron transistor (SET) consisting of parallel double quantum dots
fabricated in a GaAs/AlGaAs heterostructure crystal is
demonstrated to serve as an extremely high sensitive detector of submillimeter
waves (SMMW). One of the double dots is ionized by SMMW via Kohn-mode plasma
excitation, which affects the SET conductance through the other quantum dot
yielding the photoresponse. Noise equivalent power of the detector for
wavelengths about 0.6 mm is estimated to reach the order of
W/ at 70 mK.Comment: 3 pages, 4 figures, REVTeX, submitted to Appl.Phys.Let
Newcomers Meet the Intracluster Medium in the Coma Cluster
A main topic at this meeting is how galaxies are affected when they enter for
the first time the cluster environment from the outskirts. Most of the times we
are forced to infer the environmental effects indirectly, relying on systematic
variations of galaxy properties with environment, but there aren't many
examples of direct observations able to unveil ongoing transformations taking
place, and the corresponding mechanism producing it. We present a case in which
it is possible to identify the cluster environment, and in particular the
intracluster medium and the recent infall history of galaxies onto the cluster,
as the cause for a recent, abrupt change in the evolutionary history of
galaxies.Comment: 5 pages, 1 postscript figure -- to appear in "Outskirts of Galaxy
Clusters: intense life in the suburbs", IAU Colloquium N. 195, 2004, ed. A
Diaferi
The habitat segregation between Lyman break galaxies and Ly alpha emitters around a QSO at z similar to 5
We carried out a target survey for Lyman break galaxies ( LBGs) and Ly alpha emitters ( LAEs) around QSO SDSS J0211- 0009 at z= 4. 87. The deep and wide broadband and narrowband imaging simultaneously revealed the perspective structure of these two high- z populations. The LBGs without Ly alpha emission form a filamentary structure including the QSO, while the LAEs are distributed around the QSO but avoid it within a distance of similar to 4.5Mpc. On the other hand, we serendipitously discovered a protocluster with a significant concentration of LBGs and LAEs, where no strongly UVionizing source, such as a QSO or radio galaxy, is known to exist. In this cluster field, the two populations are spatially cross- correlated with each other. The relative spatial distribution of LAEs to LBGs in the QSO field is in stark contrast to that in the cluster field. We also found a weak trend showing that the number counts based on Ly alpha and UV continuum fluxes of LAEs in the QSO field are slightly lower than in the cluster field, whereas the number counts of LBGs are almost consistent with each other. The LAEs avoid the nearby region around the QSO where the local UV background radiation could be similar to 100 times stronger than the average for the epoch. The clustering segregation between LBGs and LAEs seen in the QSO field could be due to either enhanced early galaxy formation in an overdense environment, causing all the LAEs to evolve into LBGs, or local photoionization due to the strong UV radiation from the QSO, effectively causing a deficit in low- mass galaxies like LAEs.ArticleThe Astrophysical Journal. 663:765-773 (2007)journal articl
CSIP - a Novel Photon-Counting Detector Applicable for the SPICA Far-Infrared Instrument
We describe a novel GaAs/AlGaAs double-quantum-well device for the infrared
photon detection, called Charge-Sensitive Infrared Phototransistor (CSIP). The
principle of CSIP detector is the photo-excitation of an intersubband
transition in a QW as an charge integrating gate and the signal amplification
by another QW as a channel with very high gain, which provides us with
extremely high responsivity (10^4 -- 10^6 A/W). It has been demonstrated that
the CSIP designed for the mid-infrared wavelength (14.7 um) has an excellent
sensitivity; the noise equivalent power (NEP) of 7x10^-19 W/rHz with the
quantum efficiency of ~2%. Advantages of the CSIP against the other highly
sensitive detectors are, huge dynamic range of >10^6, low output impedance of
10^3 -- 10^4 Ohms, and relatively high operation temperature (>2K). We discuss
possible applications of the CSIP to FIR photon detection covering 35 -- 60 um
waveband, which is a gap uncovered with presently available photoconductors.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Multiple Scattering of Fractionally-Charged Quasiparticles
We employ shot noise measurements to characterize the effective charge of
quasiparticles, at filling factor nu=1/3 of the fractional quantum Hall regime,
as they scatter from an array of identical weak backscatterers. Upon
scattering, quasiparticles are known to bunch, e.g., only three e/3 charges, or
'electrons' are found to traverse a rather opaque potential barrier. We find
here that the effective charge scattered by an array of scatterers is
determined by the scattering strength of an individual scatterer and not by the
combined scattering strength of the array, which can be very small. Moreover,
we also rule out intra-edge equilibration of e/3 quasiparticles over length
scale of hundreds microns.Comment: 4 pages, 4 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
Quantum Hall line junction with impurities as a multi-slit Luttinger liquid interferometer
We report on quantum interference between a pair of counterpropagating
quantum Hall edge states that are separated by a high quality tunnel barrier.
Observed Aharonov-Bohm oscillations are analyzed in terms of resonant tunneling
between coupled Luttinger liquids that creates bound electronic states between
pairs of tunnel centers that act like interference slits. We place a lower
bound in the range of 20-40 m for the phase coherence length and directly
confirm the extended phase coherence of quantum Hall edge states.Comment: 4 pages, 3 figures, 1 tabl
SN 2016jhj at redshift 0.34: extending the Type II supernova Hubble diagram using the standard candle method
Although Type Ia supernova cosmology has now reached a mature state, it is important to develop as many independent methods as possible to understand the true nature of dark energy. Recent studies have shown that Type II supernovae (SNe II) offer such a path and could be used as alternative distance indicators. However, the majority of these studies were unable to extend the Hubble diagram above redshift z = 0.3 because of observational limitations. Here, we show that we are now ready to move beyond low redshifts and attempt high-redshift (z ≳ 0.3) SN II cosmology as a result of new-generation deep surveys such as the Subaru/Hyper Suprime-Cam survey. Applying the ´standard candle method´ to SN 2016jhj (z = 0.3398 ± 0.0002; discovered by HSC) together with a low-redshift sample, we are able to construct the highest-redshift SN II Hubble diagram to date with an observed dispersion of 0.27 mag (i.e. 12-13 per cent in distance). This work demonstrates the bright future of SN II cosmology in the coming era of large, wide-field surveys like that of the Large Synoptic Survey Telescope.Fil: de Jaeger, T.. University of California at Berkeley; Estados UnidosFil: Galbany, L.. University of Pittsburgh at Johnstown; Estados UnidosFil: Filippenko, A. V.. University of California at Berkeley; Estados UnidosFil: González Gaitán, S.. Universidad de Chile; ChileFil: Yasuda, N.. University of Tokio; JapónFil: Maeda, K.. University of Tokio; JapónFil: Tanaka, M.. University of Tokio; JapónFil: Morokuma, T.. University of Tokio; JapónFil: Moriya, T. J.. National Astronomical Observatory of Japan; JapónFil: Tominaga, N.. University of Tokyo; JapónFil: Nomoto, Ken’ichi. University of Tokyo; JapónFil: Komiyama, Y.. National Astronomical Observatory of Japan; JapónFil: Anderson, J. P.. European Southern Observatory; ChileFil: Brink, T. G.. University of California at Berkeley; Estados UnidosFil: Carlberg, R. G.. University of Toronto; CanadáFil: Folatelli, Gaston. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. University of Tokyo; JapónFil: Hamuy, M.. Universidad de Chile; ChileFil: Pignata, G.. Universidad Andrés Bello; ChileFil: Zheng, W.. University of California at Berkeley; Estados Unido
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