4,009 research outputs found
VPI-7: The First Zincosilicate Molecular Sieve Containing Three-membered T-Atom Rings
VPI-7: the first microporous zincosilicate to contain 3-membered rings (3MR) is reported
Non-Fermi liquid angle resolved photoemission lineshapes of Li0.9Mo6O17
A recent letter by Xue et al. (PRL v.83, 1235 ('99)) reports a Fermi-Liquid
(FL) angle resolved photoemission (ARPES) lineshape for quasi one-dimensional
Li0.9Mo6O17, contradicting our report (PRL v.82, 2540 ('99)) of a non-FL
lineshape in this material. Xue et al. attributed the difference to the
improved angle resolution. In this comment, we point out that this reasoning is
flawed. Rather, we find that their data have fundamental differences from other
ARPES results and also band theory.Comment: To be published as a PRL Commen
Non-fermi-liquid single particle lineshape of the quasi-one-dimensional non-CDW metal Li_{0.9}Mo_{6}O_{17} : comparison to the Luttinger liquid
We report the detailed non-Fermi liquid (NFL) lineshape of the dispersing
excitation which defines the Fermi surface (FS) for quasi-one-dimensional
Li_{0.9}Mo_{6}O_{17}. The properties of Li_{0.9}Mo_{6}O_{17} strongly suggest
that the NFL behavior has a purely electronic origin. Relative to the
theoretical Luttinger liquid lineshape, we identify significant similarities,
but also important differences.Comment: 5 pages, 3 eps figure
Two-dimensional Hubbard-Holstein bipolaron
We present a diagrammatic Monte Carlo study of the properties of the
Hubbard-Holstein bipolaron on a two-dimensional square lattice. With a small
Coulomb repulsion, U, and with increasing electron-phonon interaction, and when
reaching a value about two times smaller than the one corresponding to the
transition of light polaron to heavy polaron, the system suffers a sharp
transition from a state formed by two weakly bound light polarons to a heavy,
strongly bound on-site bipolaron. Aside from this rather conventional bipolaron
a new bipolaron state is found for large U at intermediate and large
electron-phonon coupling, corresponding to two polarons bound on
nearest-neighbor sites. We discuss both the properties of the different
bipolaron states and the transition from one state to another. We present a
phase diagram in parameter space defined by the electron-phonon coupling and U.
Our numerical method does not use any artificial approximation and can be
easily modified to other bipolaron models with longer range electron-phonon
and/or electron-electron interaction.Comment: 14 pages, 12 figure
Possible observation of parametrically amplified coherent phasons in K0.3MoO3 using time-resolved extreme-ultraviolet ARPES
We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) in the
Extreme Ultraviolet (EUV) to measure the time- and momentum-dependent
electronic structure of photo-excited K0.3MoO3. Prompt depletion of the Charge
Density Wave (CDW) condensate launches coherent oscillations of the amplitude
mode, observed as a 1.7-THz-frequency modulation of the bonding band position.
In contrast, the anti-bonding band oscillates at about half this frequency. We
attribute these oscillations to coherent excitation of phasons via parametric
amplification of phase fluctuations.Comment: 4 figure
ARPES Line Shapes in FL and non-FL Quasi-Low-Dimensional Inorganic Metals
Quasi-low-dimensional (quasi-low-D) inorganic materials are not only ideally
suited for angle resolved photoemission spectroscopy (ARPES) but also they
offer a rich ground for studying key concepts for the emerging paradigm of
non-Fermi liquid (non-FL) physics. In this article, we discuss the ARPES
technique applied to three quasi-low-D inorganic metals: a paradigm Fermi
liquid (FL) material TiTe, a well-known quasi-1D charge density wave
(CDW) material KMoO and a quasi-1D non-CDW material
LiMoO. With TiTe, we establish that a many body
theoretical interpretation of the ARPES line shape is possible. We also address
the fundamental question of how to accurately determine the {\bf k} value
from ARPES. Both KMoO and LiMoO show
quasi-1D electronic structures with non-FL line shapes. A CDW gap opening is
observed for KMoO, whereas no gap is observed for
LiMoO. We show, however, that the standard CDW theory,
even with strong fluctuations, is not sufficient to describe the non-FL line
shapes of KMoO. We argue that a Luttinger liquid (LL) model is
relevant for both bronzes, but also point out difficulties encountered in
comparing data with theory. We interpret this situation to mean that a more
complete and realistic theory is necessary to understand these data.Comment: 23 pages, including 21 figures; to appear in a special issue of J.
Elec. Spectr. Rel. Pheno
Collisions of particles in locally AdS spacetimes II Moduli of globally hyperbolic spaces
We investigate 3-dimensional globally hyperbolic AdS manifolds containing
"particles", i.e., cone singularities of angles less than along a
time-like graph . To each such space we associate a graph and a finite
family of pairs of hyperbolic surfaces with cone singularities. We show that
this data is sufficient to recover the space locally (i.e., in the neighborhood
of a fixed metric). This is a partial extension of a result of Mess for
non-singular globally hyperbolic AdS manifolds.Comment: 29 pages, 3 figures. v2: 41 pages, improved exposition. To appear,
Comm. Math. Phys. arXiv admin note: text overlap with arXiv:0905.182
Competition between Pauli and orbital effects in a charge-density wave system
We present angular dependent magneto-transport and magnetization measurements
on alpha-(ET)2MHg(SCN)4 compounds at high magnetic fields and low temperatures.
We find that the low temperature ground state undergoes two subsequent
field-induced density-wave type phase transitions above a critical angle of the
magnetic field with respect to the crystallographic axes. This new phase
diagram may be qualitatively described assuming a charge density wave ground
state which undergoes field-induced transitions due to the interplay of Pauli
and orbital effects.Comment: 11 pages, 4 figures, shown at the APS march meeting 2000, appears in
the Ph.D. thesis of J. S. Qualls (Florida State University, 1999), and
submitted to PR
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