1,969 research outputs found
Superconductivity-Induced Transfer of In-Plane Spectral Weight in Bi2Sr2CaCu2O8: Resolving a Controversy
We present a detailed analysis of the superconductivity-induced
redistribution of optical spectral weight in Bi2Sr2CaCu2O8 near optimal doping.
It confirms the previous conclusion by Molegraaf et al. (Science 66, 2239
(2002)), that the integrated low-frequency spectral weight shows an extra
increase below Tc. Since the region, where the change of the integrated
spectral weight is not compensated, extends well above 2.5 eV, this transfer is
caused by the transfer of spectral weight from interband to intraband region
and only partially by the narrowing of the intraband peak. We show that the
opposite assertion by Boris et al. (Science 304, 708 (2004)) regarding this
compound, is unlikely the consequence of any obvious discrepancies between the
actual experimental data.Comment: ReVTeX, 9 pages, 8 encapsulated postscript figures, several typo's
correcte
Anomalous a.c. resistivity effect in Nb and Sn at high static fields in the liquid helium temperature range
The a.c. susceptibilities of Nb and Sn cylinders in the normal state at temperatures below T>c have been measured. The results cannot be described by the formalism of the classical skin-effect. Therefore a formal description is given
Infrared spectroscopic study of phonons coupled to charge excitations in FeSi
From an investigation of the optical conductivity of FeSi single crystals
using FTIR spectroscopy in the frequency range from 30 to 20000 wavenumbers we
conclude that the transverse effective charge of the Fe and Si ions is
approximately 4e. Of the five optical phonons which are allowed by symmetry we
observe only four, three of which have a Fano line shape presumably resulting
from an interaction of these modes with the electronic continuum. We show that
the large oscillator strength of the phonons results from a relatively weak
coupling (lambda of the order of 0.1) of the lattice degrees of freedom to an
electronic resonance above the semiconductor gap, which is also responsible for
the large electronic polarizability of the medium.Comment: Revtex, 10 pages, 2 postscript pictures, to be published in Phys.
Rev. B Rapid Comm
In-plane optical spectral weight transfer in optimally doped BiSrCaCuO
We examine the redistribution of the in-plane optical spectral weight in the
normal and superconducting state in tri-layer \bbb (Bi2223) near optimal doping
( = 110 K) on a single crystal via infrared reflectivity and spectroscopic
ellipsometry. We report the temperature dependence of the low-frequency
integrated spectral weight for different values of the cutoff
energy . Two different model-independent analyses consistently show
that for = 1 eV, which is below the charge transfer gap,
increases below , implying the lowering of the kinetic
energy of the holes. This is opposite to the BCS scenario, but it follows the
same trend observed in the bi-layer compound \bb (Bi2212). The size of this
effect is larger in Bi2223 than in Bi2212, approximately scaling with the
critical temperature. In the normal state, the temperature dependence of
is close to up to 300 K
C-axis optical properties of high Tc cuprates
A review is given of the experimental status of the interlayer coupling
energy in the cuprates. A second c-axis plasmon is identified in the double
layer compound Y123 for various dopings. The anomalous transport properties
along the c-direction and in the planar directions are compared to model
calculations based on strongly anisotropic scattering. An excellent description
of the optical data at optimal doping is obtained if an anomalously large
anisotropy of the scattering rate between cold spots and hot spots is assumed.
This raises questions as to the physical meaning of these parameters.Comment: 4 pages, LaTeX, espcrc2.sty, 3 figures in encapsulated postscript
forma
The black hole mass distribution in early-type galaxies: cusps in HST photometry interpreted through adiabatic black hole growth
The surface brightness profiles of early-type galaxies have central cusps.
Two characteristic profile types are observed with HST: `core' profiles have a
break at a resolved radius and logarithmic cusp slope gamma < 0.3 inside that
radius; `power-law' profiles have no clear break and gamma > 0.3. With few
exceptions, galaxies with M_V
-20.5 have power-law profiles. Both profile types occur in galaxies with -22 <
M_V < -20.5. We show that these results are consistent with the hypothesis
that: (i) all early-type galaxies have black holes (BHs) that grew
adiabatically in homogeneous isothermal cores; and (ii) these `progenitor'
cores followed scaling relations similar to those of the fundamental plane.
The models studied here are the ones first proposed by Young. Models with BH
masses and progenitor cores that obey established scaling relations predict (at
Virgo) that galaxies with M_V < -21.2 have core profiles and galaxies with M_V
> -21.2 have power-law profiles. This reproduces both the sense and the
absolute magnitude of the observed transition. Intrinsic scatter in BH and
galaxy properties can explain why both types of galaxies are observed around
the transition magnitude. The observed bimodality in cusp slopes may be due to
a bimodality in M_bh/L, with rapidly rotating disky galaxies having larger
M_bh/L than slowly rotating boxy galaxies.
Application to individual galaxies with HST photometry yields a roughly
linear correlation between BH mass and V-band galaxy luminosity, log M_bh =
-1.83 + log L (solar units). This agrees with the average relation for nearby
galaxies with kinematically determined BH masses, and also with predictions
from quasar statistics (shortened abstract).Comment: 41 pages, LaTeX, with 11 PostScript figures. Submitted to the
Astronomical Journal. Postscript version also available from
http://sol.stsci.edu/~marel/abstracts/abs_R23.htm
The counterrotating core and the black hole mass of IC1459
The E3 giant elliptical galaxy IC1459 is the prototypical galaxy with a fast
counterrotating stellar core. We obtained one HST/STIS long-slit spectrum along
the major axis of this galaxy and CTIO spectra along five position angles. We
present self-consistent three-integral axisymmetric models of the stellar
kinematics, obtained with Schwarzschild's numerical orbit superposition method.
We study the dynamics of the kinematically decoupled core (KDC) in IC1459 and
we find it consists of stars that are well-separated from the rest of the
galaxy in phase space. The stars in the KDC counterrotate in a disk on orbits
that are close to circular. We estimate that the KDC mass is ~0.5% of the total
galaxy mass or ~3*10^9 Msun. We estimate the central black hole mass M_BH of
IC1459 independently from both its stellar and its gaseous kinematics. Some
complications probably explain why we find rather discrepant BH masses with the
different methods. The stellar kinematics suggest that M_BH = (2.6 +/-
1.1)*10^9 Msun (3 sigma error). The gas kinematics suggests that M_BH ~
3.5*10^8 Msun if the gas is assumed to rotate at the circular velocity in a
thin disk. If the observed velocity dispersion of the gas is assumed to be
gravitational, then M_BH could be as high as ~1.0*10^9 Msun. These different
estimates bracket the value M_BH = (1.1 +/- 0.3)*10^9 Msun predicted by the
M_BH-sigma relation. It will be an important goal for future studies to assess
the reliability of black hole mass determinations with either technique. This
is essential if one wants to interpret the correlation between the BH mass and
other global galaxy parameters (e.g. velocity dispersion) and in particular the
scatter in these correlations (believed to be only ~0.3 dex). [Abridged]Comment: 51 pages, LaTeX with 19 PostScript figures. Revised version, with
three new figures and data tables. To appear in The Astrophysical Journal,
578, 2002 October 2
Black Hole Masses and Host Galaxy Evolution of Radio-loud Active Galactic Nuclei
We report stellar velocity dispersion measurements for a sample of 28 AGN
host galaxies including our previous work. Using the mass-dispersion
() and the fundamental plane relations, we estimate the
black hole mass for a sample of 66 BL Lac objects and investigate the role of
black hole mass in the energetics of BL Lac objects. The black hole mass range
for different BL Lac spectral types is similar, . Neither X-ray nor radio luminosity correlates with black hole
mass. Low-frequency-peaked BL Lac objects have higher Eddington ratios on
average, because of either more beaming or higher intrinsic power. For the
black hole mass range , the radio
luminosity of BL Lac objects and flat-spectrum radio quasars spans over 4
orders of magnitude, with BL Lac objects being low-power AGNs. We also
investigate the evolution of host galaxies for 39 AGNs out to
with measuredstellar velocity dispersions. Comparing the mass-to-light ratio
evolution in the observed frame with population synthesis models, we find that
single burst star formation models with are
consistent with the observations. From our model, we estimated
the intrinsic mass-to-light ratio evolution in the Cousins band, , consistent with that of normal early
type galaxies.Comment: ApJ accepted, 22 pages, 11 figure
Transverse optical Josephson plasmons, equations of motion
A detailed calculation is presented of the dielectric function in
superconducttors consisting of two Josephson coupled superconducting layers per
unit cell, taking into account the effect of finite compressibility of the
electron fluid. From the model it follows, that two longitudinal, and one
transverse optical Josephson plasma resonance exist in these materials, for
electric field polarization perpendicular to the planes. The latter mode
appears as a resonance in the transverse dielectric function, and it couples
directly to the electrical field vector of infrared radiation. A shift of all
plasma frequencies, and a reduction of the intensity of the transverse optical
Josephson plasmon is shown to result from the finite compressibility of the
electron fluid.Comment: 17 pages, ReVTeX, 7 figures in eps forma
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