8,952 research outputs found
Effect of interlayer processes on the superconducting state within t-J-U model: Full Gutzwiller wave-function solution and relation to experiment
The Gutzwiller wave function solution of the -- model is considered
for the bilayer high-T superconductor by using the so-called diagrammatic
expansion method. The focus is on the influence of the interlayer effects on
the superconducting state. The chosen pairing symmetry is a mixture of
symmetry within the layers and the so-called symmetry
for the interlayer contribution. The analyzed interlayer terms reflect the
interlayer electron hopping, the interlayer exchange coupling, and the
interlayer pair hopping. The obtained results are compared with selected
experimental data corresponding to the copper-based compound Bi-2212 with two
Cu-O planes in the unit cell. For the sake of comparison, selected results for
the case of the bilayer Hubbard model are also provided. This paper complements
our recent results obtained for the single-plane high temperature cuprates [cf.
J. Spa{\l}ek, M. Zegrodnik, and J. Kaczmarczyk, Phys. Rev. B {\bf 95}, 024506
(2017)
Evidence for forward scattering and coupling to acoustic phonon modes in high-T cuprate superconductors
Recent laser angle-resolved photoemission spectroscopy studies have
established the presence of a new kink in the low-energy nodal dispersion of
BiSrCaCuO (Bi-2212). The energy scale (~8-15 meV) of
this kink appears below the maximum of the superconducting gap .
Therefore it is difficult to interpret this feature in terms of the usual
coupling to a sharp dispersionless mode. In this paper we examine
electron-phonon coupling to the in-plane acoustic phonon branch arising from
the modulation of the screened Coulomb potential. We demonstrate that such a
coupling has a strong forward scattering peak, and as a consequence, a kink
occurs in the dispersion at an energy scale shifted by the local gap
. In addition, considerations for the reduction of screening with
underdoping naturally explains the observed doping dependence of the low-energy
kink. These results point to a strong coupling to the acoustic branch which is
peaked in the forward scattering direction and has important implications for
transport and pairing in the high-T cuprates.Comment: 4.5 pages, 4 figures, Submitted to PR
Doping-dependent nodal Fermi velocity in Bi-2212 revealed by high-resolution ARPES
The improved resolution of laser-based angle-resolved photoemission
spectroscopy (ARPES) allows reliable access to fine structures in the spectrum.
We present a systematic, doping-dependent study of a recently discovered
low-energy kink in the nodal dispersion of Bi2Sr2CaCu2O8+d (Bi-2212), which
demonstrates the ubiquity and robustness of this kink in underdoped Bi-2212.
The renormalization of the nodal velocity due to this kink becomes stronger
with underdoping, revealing that the nodal Fermi velocity is non-universal, in
contrast to assumed phenomenology. This is used together with laser-ARPES
measurements of the gap velocity, v2, to resolve discrepancies with thermal
conductivity measurements.Comment: Submitted to Phys. Rev. Let
Flow profiling of a surface acoustic wave nanopump
The flow profile in a capillary gap and the pumping efficiency of an acoustic
micropump employing Surface Acoustic Waves is investigated both experimentally
and theoretically. Such ultrasonic surface waves on a piezoelectric substrate
strongly couple to a thin liquid layer and generate an internal streaming
within the fluid. Such acoustic streaming can be used for controlled agitation
during, e.g., microarray hybridization. We use fluorescence correlation
spectroscopy and fluorescence microscopy as complementary tools to investigate
the resulting flow profile. The velocity was found to depend on the applied
power somewhat weaker than linearly and to decrease fast with the distance from
the ultrasound generator on the chip.Comment: 12 pages 20 figure
Highly anisotropic interlayer magnetoresistance in ZrSiS nodal-line Dirac semimetal
We instigate the angle-dependent magnetoresistance (AMR) of the layered
nodal-line Dirac semimetal ZrSiS for the in-plane and out-of-plane current
directions. This material has recently revealed an intriguing butterfly-shaped
in-plane AMR that is not well understood. Our measurements of the polar
out-of-plane AMR show a surprisingly different response with a pronounced
cusp-like feature. The maximum of the cusp-like anisotropy is reached when the
magnetic field is oriented in the - plane. Moreover, the AMR for the
azimuthal out-of-plane current direction exhibits a very strong four-fold
- plane anisotropy. Combining the Fermi surfaces calculated from first
principles with the Boltzmann's semiclassical transport theory we reproduce and
explain all the prominent features of the unusual behavior of the in-plane and
out-of-plane AMR. We are also able to clarify the origin of the strong
non-saturating transverse magnetoresistance as an effect of imperfect
charge-carrier compensation and open orbits. Finally, by combining our
theoretical model and experimental data we estimate the average relaxation time
of ~s and the mean free path of ~nm at 1.8~K in our
samples of ZrSiS.Comment: 8 pages, 4 figure
Site-Dilution in quasi one-dimensional antiferromagnet Sr2(Cu1-xPdx)O3: reduction of Neel Temperature and spatial distribution of ordered moment sizes
We investigate the Neel temperature of Sr2CuO3 as a function of the site
dilution at the Cu (S=1/2) sites with Pd (S=0), utilizing the muon spin
relaxation (muSR) technique. The Neel temperature, which is Tn=5.4K for the
undoped system, becomes significantly reduced for less than one percent of
doping Pd, giving a support for the previous proposal for the good
one-dimensionality. The Pd concentration dependence of the Neel temperature is
compared with a recent theoretical study (S. Eggert, I. Affleck and M.D.P.
Horton, Phys. Rev. Lett. 89, 47202 (2002)) of weakly coupled one-dimensional
antiferromagnetic chains of S=1/2 spins, and a quantitative agreement is found.
The inhomogeneity of the ordered moment sizes is characterized by the muSR time
spectra. We propose a model that the ordered moment size recovers away from the
dopant S=0 sites with a recovery length of \xi = 150-200 sites. The origin of
the finite recovery length \xi for the gapless S=1/2 antiferromagnetic chain is
compared to the estimate based on the effective staggered magnetic field from
the neighboring chains.Comment: 10 pages, 9 figures, submitted to PR
Change Detection Of Cropping Pattern In Paddy Field Using Multi Spectral Satellite Data For Estimating Irrigation Water Needed
This paper investigates the use of multi spectral satellite data for cropping pattern monitoring in paddy field. The southern coastal of Citarum watershed, West Java Province was selected as study sites. The analysis used in this study is identifying crop pattern based on growth stages of wetland paddy and other crops by investigating the characteristic of Normalized Difference Vegetation Indices (NDVI) and Wetness of Tasseled Cap Transformation (TCT) derived from 14 scenes of Landsat TM date 1988 to 2001. In general, the phenological of growth stages of wetland paddy can be used to distinguish with other seasonal crops. The research results indicate that multi spectral satellite data has a great potential for identification and monitoring cropping pattern in paddy field. Specific character of NDVI and Wetness also can produce a map of cropping pattern in paddy field that is useful to monitor agricultural land condition. The cropping pattern can also be used to estimate irrigation water needed of paddy field in the area. Expected implication of the information obtained from this analysis is useful for guidance more appropriate planning and better management of agricultural
New Josephson Plasma Modes in Underdoped YBa2Cu3O6.6 Induced by Parallel Magnetic Field
The c-axis reflectivity spectrum of underdoped YBa2Cu3O6.6 (YBCO) is measured
below Tc=59K in parallel magnetic fields H//CuO2 up to 7T. Upon application of
a parallel field, a new peak appears at finite frequency in the optical
conductivity at the expense of suppression of c-axis condensate weight. We
conclude that the dramatic change originates from different Josephson coupling
strengths between bilayers with and without Josephson vortices. We find that
the 400cm^-1 broad conductivity peak in YBCO gains the spectral weight under
parallel magnetic field; this indicates that the condensate weight at \omega =0
is distributed to the intra-bilayer mode as well as to the new optical
Josephson mode.Comment: 4 pages, 3 figure
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