1,841 research outputs found
Origin of time reversal symmetry breaking in Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x)
We have studied the Zero Bias Conductance Peak (ZBCP) of the tunneling
conductance measured on (1,1,0) oriented Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x) thin films
as a function of doping and of magnetic field. A spontaneous (zero field) split
of the ZBCP was observed only in overdoped samples (either by O or by Ca). The
magnitude of this split was found to be linear in doping. All samples exhibited
a magnetic field splitting, also strongly doping dependent. The field
susceptibility chi=d(delta)/dH diverges at the point at which spontaneous ZBCP
splitting occurs, its inverse value, chi^(-1), following a linear doping
dependence on both the underdoped and overdoped sides. We discuss these results
in terms of recent theoretical models of Time Reversal Symmetry Breaking
(TRSB).Comment: 5 figure
Shubnikov-de Haas oscillations in SrTiO3\LaAlO3 interface
Quantum magnetic oscillations in SrTiO3/\LaAlO3 interface are observed. The
evolution of their frequency and amplitude at various gate voltages and
temperatures is studied. The data are consistent with the Shubnikov de-Haas
theory. The Hall resistivity rho exhibits nonlinearity at low magnetic field.
It is fitted assuming multiple carrier contributions. The comparison between
the mobile carrier density inferred from the Hall data and the oscillation
frequency suggests multiple valley and spin degeneracy. The small amplitude of
the oscillations is discussed in the framework of the multiple band scenario
Tuning spin-orbit coupling and superconductivity at the SrTiO3/LaAlO3 interface: a magneto-transport study
The superconducting transition temperature, Tc, of the SrTiO3/LaAlO3
interface was varied by the electric field effect. The anisotropy of the upper
critical field and the normal state magneto-transport were studied as a
function of gate voltage. The spin-orbit coupling energy is extracted. This
tunable energy scale is used to explain the strong gate dependence of the
mobility and of the anomalous Hall signal observed. The spin-orbit coupling
energy follows Tc for the electric field range under study
Role of oxygen in the electron-doped superconducting cuprates
We report on resistivity and Hall measurements in thin films of the
electron-doped superconducting cuprate PrCeCuO.
Comparisons between x = 0.17 samples subjected to either ion-irradiation or
oxygenation demonstrate that changing the oxygen content has two separable
effects: 1) a doping effect similar to that of cerium, and 2) a disorder
effect. These results are consistent with prior speculations that apical oxygen
removal is necessary to achieve superconductivity in this compound.Comment: 5 pages, 5 figure
Phase coherent transport in SrTiO3/LaAlO3 interfaces
The two dimensional electron gas formed between the two band insulators
SrTiO3 and LaAlO3 exhibits a variety of interesting physical properties which
make it an appealing material for use in future spintronics and/or quantum
computing devices. For this kind of applications electrons have to retain their
phase memory for sufficiently long times or length. Using a mesoscopic size
device we were able to extract the phase coherence length, and its temperature
variation. We find the dephasing rate to have a power law dependence on
temperature. The power depends on the temperature range studied and sheet
resistance as expected from dephasing due to strong electron-electron
interactions.Comment: Submitted to Phys. Rev
SciRecSys: A Recommendation System for Scientific Publication by Discovering Keyword Relationships
In this work, we propose a new approach for discovering various relationships
among keywords over the scientific publications based on a Markov Chain model.
It is an important problem since keywords are the basic elements for
representing abstract objects such as documents, user profiles, topics and many
things else. Our model is very effective since it combines four important
factors in scientific publications: content, publicity, impact and randomness.
Particularly, a recommendation system (called SciRecSys) has been presented to
support users to efficiently find out relevant articles
Use of groundwater lifetime expectancy for the performance assessment of a deep geologic waste repository: 1. Theory, illustrations, and implications
Long-term solutions for the disposal of toxic wastes usually involve
isolation of the wastes in a deep subsurface geologic environment. In the case
of spent nuclear fuel, if radionuclide leakage occurs from the engineered
barrier, the geological medium represents the ultimate barrier that is relied
upon to ensure safety. Consequently, an evaluation of radionuclide travel times
from a repository to the biosphere is critically important in a performance
assessment analysis. In this study, we develop a travel time framework based on
the concept of groundwater lifetime expectancy as a safety indicator. Lifetime
expectancy characterizes the time that radionuclides will spend in the
subsurface after their release from the repository and prior to discharging
into the biosphere. The probability density function of lifetime expectancy is
computed throughout the host rock by solving the backward-in-time solute
transport adjoint equation subject to a properly posed set of boundary
conditions. It can then be used to define optimal repository locations. The
risk associated with selected sites can be evaluated by simulating an
appropriate contaminant release history. The utility of the method is
illustrated by means of analytical and numerical examples, which focus on the
effect of fracture networks on the uncertainty of evaluated lifetime
expectancy.Comment: 11 pages, 8 figures; Water Resources Research, Vol. 44, 200
Horizontally transmitted symbiont populations in deep-sea mussels are genetically isolated
Eukaryotes are habitats for bacterial organisms where the host colonization and dispersal among individual hosts have consequences for the bacterial ecology and evolution. Vertical symbiont transmission leads to geographic isolation of the microbial population and consequently to genetic isolation of microbiotas from individual hosts. In contrast, the extent of geographic and genetic isolation of horizontally transmitted microbiota is poorly characterized. Here we show that chemosynthetic symbionts of individual Bathymodiolus brooksi mussels constitute genetically isolated subpopulations. The reconstruction of core genome-wide strains from high-resolution metagenomes revealed distinct phylogenetic clades. Nucleotide diversity and strain composition vary along the mussel life span and individual hosts show a high degree of genetic isolation. Our results suggest that the uptake of environmental bacteria is a restricted process in B. brooksi, where self-infection of the gill tissue results in serial founder effects during symbiont evolution. We conclude that bacterial colonization dynamics over the host life cycle is thus an important determinant of population structure and genome evolution of horizontally transmitted symbionts
- …