20,633 research outputs found
Directed flow as effect of transient matter rotation in hadron and nucleus collisions
We discuss directed flow introduced for description of nucleus collisions and
consider its possible behavior in hadronic and nuclei reactions due to rotation
of the transient matter.Comment: 18 pages, 6 figure
Phase control of La2CuO4 in thin-film synthesis
The lanthanum copper oxide, La2CuO4, which is an end member of the prototype
high-Tc superconductors (La,Sr)2CuO4 and (La,Ba)2CuO4, crystallizes in the
"K2NiF4" structure in high-temperature bulk synthesis. The crystal chemistry,
however, predicts that La2CuO4 is at the borderline of the K2NiF4 stability and
that it can crystallize in the Nd2CuO4 structure at low synthesis temperatures.
In this article we demonstrate that low-temperature thin-film synthesis
actually crystallizes La2CuO4 in the Nd2CuO4 structure. We also show that the
phase control of "K2NiF4"-type La2CuO4 versus "Nd2CuO4"-type La2CuO4 can be
achieved by varying the synthesis temperature and using different substrates.Comment: 4 pages, 5 figures, submitted to PRB, revte
General linear dynamics - quantum, classical or hybrid
We describe our recent proposal of a path integral formulation of classical
Hamiltonian dynamics. Which leads us here to a new attempt at hybrid dynamics,
which concerns the direct coupling of classical and quantum mechanical degrees
of freedom. This is of practical as well as of foundational interest and no
fully satisfactory solution of this problem has been established to date.
Related aspects will be observed in a general linear ensemble theory, which
comprises classical and quantum dynamics in the form of Liouville and von
Neumann equations, respectively, as special cases. Considering the simplest
object characterized by a two-dimensional state-space, we illustrate how
quantum mechanics is special in several respects among possible linear
generalizations.Comment: 17 pages; based on invited talks at the conferences DICE2010
(Castiglioncello, Italia, Sept 13-17, 2010) and Quantum Field Theory and
Gravity (Regensburg, Germany, Sept 28 - Oct 1, 2010
Variational Thomas-Fermi Theory of a Nonuniform Bose Condensate at Zero Temperature
We derive a description of the spatially inhomogeneous Bose-Einstein
condensate which treats the system locally as a homogeneous system. This
approach, similar to the Thomas-Fermi model for the inhomogeneous many-particle
fermion system, is well-suited to describe the atomic Bose-Einstein condensates
that have recently been obtained experimentally through atomic trapping and
cooling. In this paper, we confine our attention to the zero temperature case,
although the treatment can be generalized to finite temperatures, as we shall
discuss elsewhere.Comment: 24 pages, latex, 6 ps figures, BoxedEPS include
Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2
The sodium cobaltate family (NaxCoO2) is unique among transition metal oxides
because the Co sits on a triangular lattice and its valence can be tuned over a
wide range by varying the Na concentration x. Up to now detailed modeling of
the rich phenomenology (which ranges from unconventional superconductivity to
enhanced thermopower) has been hampered by the difficulty of controlling pure
phases. We discovered that certain Na concentrations are specially stable and
are associated with superlattice ordering of the Na clusters. This leads
naturally to a picture of co-existence of localized spins and itinerant charge
carriers. For x = 0.84 we found a remarkably small Fermi energy of 87 K. Our
picture brings coherence to a variety of measurements ranging from NMR to
optical to thermal transport. Our results also allow us to take the first step
towards modeling the mysterious ``Curie-Weiss'' metal state at x = 0.71. We
suggest the local moments may form a quantum spin liquid state and we propose
experimental test of our hypothesis.Comment: 16 pages, 5 figure
Doping evolution of the electronic structure in the single-layer cuprates BiSrLaCuO: Comparison with other single-layer cuprates
We have performed angle-resolved photoemission and core-level x-ray
photoemission studies of the single-layer cuprate
BiSrLaCuO (Bi2201) and revealed the doping
evolution of the electronic structure from the lightly-doped to optimally-doped
regions. We have observed the formation of the dispersive quasi-particle band,
evolution of the Fermi ``arc'' into the Fermi surface and the shift of the
chemical potential with hole doping as in other cuprates. The doping evolution
in Bi2201 is similar to that in CaNaCuOCl (Na-CCOC),
where a rapid chemical potential shift toward the lower Hubbard band of the
parent insulator has been observed, but is quite different from that in
LaSrCuO (LSCO), where the chemical potential does not
shift, yet the dispersive band and the Fermi arc/surface are formed around the
Fermi level already in the lightly-doped region. The (underlying) Fermi surface
shape and band dispersions are quantitatively analyzed using tight-binding fit,
and the deduced next-nearest-neighbor hopping integral also confirm the
similarity to Na-CCOC and the difference from LSCO
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