1,920 research outputs found
Stripe Disordering Transition
We have recently begun Monte Carlo simulations of the dynamics of stripe
phases in the cuprates. A simple model of spinodal decomposition of the holes
allows us to incorporate Coulomb repulsion and coherency strains. We find
evidence for a possible stripe disordering transition, at a temperature below
the pseudogap onset. Experimental searches for such a transition can provide
constraints for models of stripe formation.Comment: 4 pages LaTex, 2 ps figures (U. of Miami Conference HTS99
Evolution of Mid-gap States and Residual 3-Dimensionality in LaSrCuO
We have carried out extensive first principles doping-dependent computations
of angle-resolved photoemission (ARPES) intensities in LaSrCuO
(LSCO) over a wide range of binding energies. Intercell hopping and the
associated 3-dimensionality, which is usually neglected in discussing cuprate
physics, is shown to play a key role in shaping the ARPES spectra. Despite the
obvious importance of strong coupling effects (e.g. the presence of a lower
Hubbard band coexisting with mid-gap states in the doped insulator), we show
that a number of salient features of the experimental ARPES spectra are
captured to a surprisingly large extent when effects of -dispersion are
properly included in the analysis.Comment: 5 pages, 4 figure
Nodeless d-wave superconducting pairing due to residual antiferromagnetism in underdoped PrCeCuO
We have investigated the doping dependence of the penetration depth vs.
temperature in electron doped PrCeCuO using a model
which assumes the uniform coexistence of (mean-field) antiferromagnetism and
superconductivity. Despite the presence of a pairing gap in the
underlying spectrum, we find nodeless behavior of the low- penetration depth
in underdoped case, in accord with experimental results. As doping increases, a
linear-in- behavior of the penetration depth, characteristic of d-wave
pairing, emerges as the lower magnetic band crosses the Fermi level and creates
a nodal Fermi surface pocket.Comment: Accepted in PRL for publicatio
Noisy metrology beyond the standard quantum limit
Parameter estimation is of fundamental importance in areas from atomic
spectroscopy and atomic clocks to gravitational wave detection. Entangled
probes provide a significant precision gain over classical strategies in the
absence of noise. However, recent results seem to indicate that any small
amount of realistic noise restricts the advantage of quantum strategies to an
improvement by at most a multiplicative constant. Here, we identify a relevant
scenario in which one can overcome this restriction and attain superclassical
precision scaling even in the presence of uncorrelated noise. We show that
precision can be significantly enhanced when the noise is concentrated along
some spatial direction, while the Hamiltonian governing the evolution which
depends on the parameter to be estimated can be engineered to point along a
different direction. In the case of perpendicular orientation, we find
superclassical scaling and identify a state which achieves the optimum.Comment: Erroneous expressions with inconsistent units have been corrected. 5
pages, 3 figures + Appendi
A competing order scenario of two-gap behavior in hole doped cuprates
Angle-dependent studies of the gap function provide evidence for the
coexistence of two distinct gaps in hole doped cuprates, where the gap near the
nodal direction scales with the superconducting transition temperature ,
while that in the antinodal direction scales with the pseudogap temperature. We
present model calculations which show that most of the characteristic features
observed in the recent angle-resolved photoemission spectroscopy (ARPES) as
well as scanning tunneling microscopy (STM) two-gap studies are consistent with
a scenario in which the pseudogap has a non-superconducting origin in a
competing phase. Our analysis indicates that, near optimal doping,
superconductivity can quench the competing order at low temperatures, and that
some of the key differences observed between the STM and ARPES results can give
insight into the superlattice symmetry of the competing order.Comment: 9 pages, 7 fig
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