4,481 research outputs found
Paramagnon-induced dispersion anomalies in the cuprates
We report the self-energy associated with RPA magnetic susceptibility in the
hole-doped Bi_2Sr_2CuO_6 (Bi2201) and the electron-doped Nd_{2-x}Ce_xCuO_4
(NCCO) in the overdoped regime within the framework of a one-band Hubbard
model. Strong weight is found in the magnetic spectrum around (pi, 0) at about
360 meV in Bi2201 and 640 meV in NCCO, which yields dispersion anomalies in
accord with the recently observed `waterfall' effects in the cuprates.Comment: Submitted to PRL, Dec. 21, 2006; 4 eps figures, revte
Itinerant ferromagnetism in a two-dimensional atomic gas
Motivated by the first experimental evidence of ferromagnetic behavior in a
three-dimensional ultracold atomic gas, we explore the possibility of itinerant
ferromagnetism in a trapped two-dimensional atomic gas. Firstly, we develop a
formalism that demonstrates how quantum fluctuations drive the ferromagnetic
reconstruction first order, and consider the consequences of an imposed
population imbalance. Secondly, we adapt this formalism to elucidate the key
experimental signatures of ferromagnetism in a realistic trapped geometry.Comment: Accepted for publication in Phys. Rev.
Thomas-Ehrman shifts in nuclei around ^{16}O and role of residual nuclear interaction
The asymmetry in the energy spectra between mirror nuclei (the Thomas-Ehrman
shifts) around O is investigated from a phenomenological viewpoint. The
recent data on proton-rich nuclei indicates that the residual nuclear
interaction is reduced for the loosely bound s-orbit by as much as 30%, which
originates in the broad radial distribution of the proton single-particle wave
function.Comment: to appear in Phys. Lett. B, with 3 eps figure
SU(N) Coherent States and Irreducible Schwinger Bosons
We exploit the SU(N) irreducible Schwinger boson to construct SU(N) coherent
states. This construction of SU(N) coherent state is analogous to the
construction of the simplest Heisenberg-Weyl coherent states. The coherent
states belonging to irreducible representations of SU(N) are labeled by the
eigenvalues of the SU(N) Casimir operators and are characterized by
complex orthonormal vectors describing the SU(N) group manifold.Comment: 12 pages, 3 figure
Spin 3/2 dimer model
We present a parent Hamiltonian for weakly dimerized valence bond solid
states for arbitrary half-integral S. While the model reduces for S=1/2 to the
Majumdar-Ghosh Hamiltonian we discuss this model and its properties for S=3/2.
Its degenerate ground state is the most popular toy model state for discussing
dimerization in spin 3/2 chains. In particular, it describes the impurity
induced dimer phase in Cr8Ni as proposed recently. We point out that the
explicit construction of the Hamiltonian and its main features apply to
arbitrary half-integral spin S.Comment: 5+ pages, 6 figures; to appear in Europhysics Letter
Addendum to: Capillary floating and the billiard ball problem
We compare the results of our earlier paper on the floating in neutral
equilibrium at arbitrary orientation in the sense of Finn-Young with the
literature on its counterpart in the sense of Archimedes. We add a few remarks
of personal and social-historical character.Comment: This is an addendum to my article Capillary floating and the billiard
ball problem, Journal of Mathematical Fluid Mechanics 14 (2012), 363 -- 38
Phase-space characterization of complexity in quantum many-body dynamics
We propose a phase-space Wigner harmonics entropy measure for many-body
quantum dynamical complexity. This measure, which reduces to the well known
measure of complexity in classical systems and which is valid for both pure and
mixed states in single-particle and many-body systems, takes into account the
combined role of chaos and entanglement in the realm of quantum mechanics. The
effectiveness of the measure is illustrated in the example of the Ising chain
in a homogeneous tilted magnetic field. We provide numerical evidence that the
multipartite entanglement generation leads to a linear increase of entropy
until saturation in both integrable and chaotic regimes, so that in both cases
the number of harmonics of the Wigner function grows exponentially with time.
The entropy growth rate can be used to detect quantum phase transitions. The
proposed entropy measure can also distinguish between integrable and chaotic
many-body dynamics by means of the size of long term fluctuations which become
smaller when quantum chaos sets in.Comment: 10 pages, 9 figure
Critical properties and Bose Einstein Condensation in dimer spin systems
We analyze the spin relaxation time for a system made of weakly
coupled one dimensional ladders.This system allows to probe the dimensional
crossover between a Luttinger liquid and a Bose-Einstein condensateof magnons.
We obtain the temperature dependence of in the various dimensional
regimes, and discuss the experimental consequences.Comment: 4 pages, RevTeX 4, 3 EPS figure
Intra-Landau level Cyclotron Resonance in Bilayer Graphene
Interaction driven integer quantum Hall effects are anticipated in graphene
bilayers because of the near-degeneracy of the eight Landau levels which appear
near the neutral system Fermi level. We predict that an intra-Landau-level
cyclotron resonance signal will appear at some odd-integer filling factors,
accompanied by collective modes which are nearly gapless and have approximate
dispersion. We speculate on the possibility of unususal localization
physics associated with these modes.Comment: 5 pages, 2 figure
Routes towards Anderson-Like localization of Bose-Einstein condensates in disordered optical lattices
We investigate, both experimentally and theoretically, possible routes
towards Anderson-like localization of Bose-Einstein condensates in disordered
potentials. The dependence of this quantum interference effect on the nonlinear
interactions and the shape of the disorder potential is investigated.
Experiments with an optical lattice and a superimposed disordered potential
reveal the lack of Anderson localization. A theoretical analysis shows that
this absence is due to the large length scale of the disorder potential as well
as its screening by the nonlinear interactions. Further analysis shows that
incommensurable superlattices should allow for the observation of the
cross-over from the nonlinear screening regime to the Anderson localized case
within realistic experimental parameters.Comment: 4 pages to appear in Phys. Rev. Let
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