41,344 research outputs found
Competing Ground States in Triple-layered Sr4Ru3O10: Verging on Itinerant Ferromagnetism with Critical Fluctuations
Sr4Ru3O10 is characterized by a sharp metamagnetic transition and
ferromagnetic behavior occurring within the basal plane and along the c-axis,
respectively. Resistivity at magnetic field, B, exhibits low-frequency quantum
oscillations when B||c-axis and large magnetoresistivity accompanied by
critical fluctuations driven by the metamagnetism when B^c-axis. The complex
behavior evidenced in resistivity, magnetization and specific heat presented is
not characteristic of any obvious ground states, and points to an exotic state
that shows a delicate balance between fluctuations and order.Comment: 18 pages, 4 figure
Destruction of the Mott Insulating Ground State of Ca_2RuO_4 by a Structural Transition
We report a first-order phase transition at T_M=357 K in single crystal
Ca_2RuO_4, an isomorph to the superconductor Sr_2RuO_4. The discontinuous
decrease in electrical resistivity signals the near destruction of the Mott
insulating phase and is triggered by a structural transition from the low
temperature orthorhombic to a high temperature tetragonal phase. The magnetic
susceptibility, which is temperature dependent but not Curie-like decreases
abruptly at TM and becomes less temperature dependent. Unlike most insulator to
metal transitions, the system is not magnetically ordered in either phase,
though the Mott insulator phase is antiferromagnetic below T_N=110 K.Comment: Accepted for publication in Phys. Rev. B (Rapid Communications
Quantum -core conduction on the Bethe lattice
Classical and quantum conduction on a bond-diluted Bethe lattice is
considered. The bond dilution is subject to the constraint that every occupied
bond must have at least neighboring occupied bonds, i.e. -core
diluted. In the classical case, we find the onset of conduction for is
continuous, while for , the onset of conduction is discontinuous with the
geometric random first-order phase transition driving the conduction
transition. In the quantum case, treating each occupied bond as a random
scatterer, we find for that the random first-order phase transition in
the geometry also drives the onset of quantum conduction giving rise to a new
universality class of Anderson localization transitions.Comment: 12 pgs., 6 fig
Medium polarization in asymmetric nuclear matter
The influence of the core polarization on the effective nuclear interaction
of asymmetric nuclear matter is calculated in the framework of the induced
interaction theory. The strong isospin dependence of the density and spin
density fluctuations is studied along with the interplay between the neutron
and proton core polarizations. Moving from symmetric nuclear matter to pure
neutron matter the crossover of the induced interaction from attractive to
repulsive in the spin singlet state is determined as a function of the isospin
imbalance.The density range in which it occurs is also determined. For the spin
triplet state the induced interaction turns out to be always repulsive. The
implications of the results for the neutron star superfluid phases are shortly
discussed.Comment: 6 pages, 4 figure
Gravitational lensing effects on sub-millimetre galaxy counts
We study the effects on the number counts of sub-millimetre galaxies due to
gravitational lensing. We explore the effects on the magnification cross
section due to halo density profiles, ellipticity and cosmological parameter
(the power-spectrum normalisation ). We show that the ellipticity
does not strongly affect the magnification cross section in gravitational
lensing while the halo radial profiles do. Since the baryonic cooling effect is
stronger in galaxies than clusters, galactic haloes are more concentrated. In
light of this, a new scenario of two halo population model is explored where
galaxies are modeled as a singular isothermal sphere profile and clusters as a
Navarro, Frenk and White (NFW) profile. We find the transition mass between the
two has modest effects on the lensing probability. The cosmological parameter
alters the abundance of haloes and therefore affects our results.
Compared with other methods, our model is simpler and more realistic. The
conclusions of previous works is confirm that gravitational lensing is a
natural explanation for the number count excess at the bright end.Comment: 10 pages, 10 figures, accepted by MNRA
Orbitally-driven Behavior: Mott Transition, Quantum Oscillations and Colossal Magnetoresistance in Bilayered Ca3Ru2O7
We report recent transport and thermodynamic experiments over a wide range of
temperatures for the Mott-like system Ca3Ru2O7 at high magnetic fields, B, up
to 30 T. This work reveals a rich and highly anisotropic phase diagram, where
applying B along the a-, b-, and c-axis leads to vastly different behavior. A
fully spin-polarized state via a first order metamagnetic transition is
obtained for B||a, and colossal magnetoresistance is seen for B||b, and quantum
oscillations in the resistivity are observed for B||c, respectively. The
interplay of the lattice, orbital and spin degrees of freedom are believed to
give rise to this strongly anisotropic behavior.Comment: 26 pages and 8 figure
Evolution of Magnetism in Single-Crystal Honeycomb Iridates
We report the successful synthesis of single-crystals of the layered iridate,
(NaLi)IrO, , and a thorough study of
its structural, magnetic, thermal and transport properties. The new compound
allows a controlled interpolation between NaIrO and LiIrO,
while maintaing the novel quantum magnetism of the honeycomb Ir planes.
The measured phase diagram demonstrates a dramatic suppression of the N\'eel
temperature, , at intermediate suggesting that the magnetic order in
NaIrO and LiIrO are distinct, and that at , the
compound is close to a magnetically disordered phase that has been sought after
in NaIrO and LiIrO. By analyzing our magnetic data with a
simple theoretical model we also show that the trigonal splitting, on the
Ir ions changes sign from NaIrO and LiIrO, and the
honeycomb iridates are in the strong spin-orbit coupling regime, controlled by
\jeff=1/2 moments.Comment: updated version with more dat
Shaping of molecular weight distribution by iterative learning probability density function control strategies
A mathematical model is developed for the molecular weight distribution (MWD) of free-radical styrene polymerization in a simulated semi-batch reactor system. The generation function technique and moment method are employed to establish the MWD model in the form of Schultz-Zimmdistribution. Both static and dynamic models are described in detail. In order to achieve the closed-loop MWD shaping by output probability density function (PDF) control, the dynamic MWD model is further developed by a linear B-spline approximation. Based on the general form of the B-spline MWD model, iterative learning PDF control strategies have been investigated in order to improve the MWD control performance. Discussions on the simulation studies show the advantages and limitations of the methodology
Level statistics for quantum -core percolation
Quantum -core percolation is the study of quantum transport on -core
percolation clusters where each occupied bond must have at least occupied
neighboring bonds. As the bond occupation probability, , is increased from
zero to unity, the system undergoes a transition from an insulating phase to a
metallic phase. When the lengthscale for the disorder, , is much greater
than the coherence length, , earlier analytical calculations of quantum
conduction on the Bethe lattice demonstrate that for the metal-insulator
transition (MIT) is discontinuous, suggesting a new universality class of
disorder-driven quantum MITs. Here, we numerically compute the level spacing
distribution as a function of bond occupation probability and system size
on a Bethe-like lattice. The level spacing analysis suggests that for ,
, the quantum percolation critical probability, is greater than , the
geometrical percolation critical probability, and the transition is continuous.
In contrast, for , and the transition is discontinuous such that
these numerical findings are consistent with our previous work to reiterate a
new universality class of disorder-driven quantum MITs.Comment: 8 pages, 11 figure
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