6,709 research outputs found
Variational Studies of Triangular Heisenberg Antiferromagnet in Magnetic Field
We present a variational study of the Heisenberg antiferromagnet on the
spatially anisotropic triangular lattice in magnetic field. First we construct
a simple yet accurate wavefunction for the 1/3-magnetization plateau uud phase
on the isotropic lattice. Beginning with this state, we obtain natural
extensions to nearby commensurate coplanar phases on either side of the
plateau. The latter occur also for low lattice anisotropy, while the uud state
extends to much larger anisotropy. Far away from the 1/3 plateau and for
significant anisotropy, incommensurate states have better energetics, and we
address competition between coplanar and non-coplanar states in the high field
regime. For very strong anisotropy, our study is dominated by quasi-1d physics.
The variational study is supplemented by exact diagonalization calculations
which provide a reference for testing the energetics of our trial wavefunctions
as well as helping to identify candidate phases.Comment: 15 pages, 11 figure
Two distinct topological phases in the mixed valence compound YbB6 and its differences from SmB6
We discuss the evolution of topological states and their orbital textures in
the mixed valence compounds SmB6 and YbB6 within the framework of the
generalized gradient approximation plus onsite Coulomb interaction (GGA+U)
scheme for a wide range of values of U. In SmB6, the topological Kondo
insulator (TKI) gap is found to be insensitive to the value of U, but in sharp
contrast, Kondo physics in isostructural YbB6 displays a surprising sensitivity
to U. In particular, as U is increased in YbB6, the correlated TKI state in the
weak-coupling regime transforms into a d-p-type topological insulator phase
with a band inversion between Yb-5d and B-2p orbitals in the intermediate
coupling range, without closing the insulating energy gap throughout this
process. Our theoretical predictions related to the TKI and non-TKI phases in
SmB6 and YbB6 are in substantial accord with recent angle-resolved
photoemission spectroscopy (ARPES) experiments.Comment: 6 pages, 4 figures URL:
http://link.aps.org/doi/10.1103/PhysRevB.91.15515
Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition
We consider the motion of red blood cells and other non-spherical
microcapsules dilutely suspended in a simple shear flow. Our analysis indicates
that depending on the viscosity, membrane elasticity, geometry and shear rate,
the particle exhibits either tumbling, tank-treading of the membrane about the
viscous interior with periodic oscillations of the orientation angle, or
intermittent behavior in which the two modes occur alternately. For red blood
cells, we compute the complete phase diagram and identify a novel
tank-treading-to-tumbling transition at low shear rates. Observations of such
motions coupled with our theoretical framework may provide a sensitive means of
assessing capsule properties.Comment: 11 pages, 4 figure
Technique sensitivity in bonding to acid-etched dentin
Abstract no. 14published_or_final_versio
Two modes of nanoleakage expression in single-step adhesives
published_or_final_versio
Swinging of red blood cells under shear flow
We reveal that under moderate shear stress (of the order of 0.1 Pa) red blood
cells present an oscillation of their inclination (swinging) superimposed to
the long-observed steady tanktreading (TT) motion. A model based on a fluid
ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape
memory) predicts all observed features of the motion: an increase of both
swinging amplitude and period (1/2 the TT period) upon decreasing the shear
stress, a shear stress-triggered transition towards a narrow shear stress-range
intermittent regime of successive swinging and tumbling, and a pure tumbling
motion at lower shear stress-values.Comment: 4 pages 5 figures submitted to Physical Review Letter
Non-Kondo-like Electronic Structure in the Correlated Rare-Earth Hexaboride YbB
We present angle-resolved photoemission studies on the rare-earth hexaboride
YbB, which has recently been predicted to be a topological Kondo insulator.
Our data do not agree with the prediction and instead show that YbB
exhibits a novel topological insulator state in the absence of a Kondo
mechanism. We find that the Fermi level electronic structure of YbB has
three 2D Dirac cone like surface states enclosing the Kramers' points, while
the f-orbital which would be relevant for the Kondo mechanism is eV
below the Fermi level. Our first-principles calculation shows that the
topological state which we observe in YbB is due to an inversion between Yb
and B bands. These experimental and theoretical results provide a new
approach for realizing novel correlated topological insulator states in
rare-earth materials.Comment: 5 pages, 4 figures, Submitted in 2014. Published in 2015, Phys. Rev.
Lett. 114, 01640
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