5,196 research outputs found
The "Strange Metal" is a Projected Fermi Liquid with Edge Singularities
The puzzling "strange metal" phase of the high Tc cuprate phase diagram
reveals itself as closer to a Fermi liquid than previously supposed: it is a
consequence of Gutzwiller projection and does not necessarily require exotica
such as an RVB or mysterious quantum critical points. There is a Fermi
liquid-like excitation spectrum but the excitations are asymmetric between
electrons and holes, show anomalous forward scattering and have Z equal to 0.
We explain the power law dependence of conductivity on frequency and predict
anomalies in the tunneling and photoemission spectra.Comment: replaced tocorrect a math error in a later section, to clarify
exposition, and to add references to more experiment
Superfluid Transition in a Chiron Gas
Low temperature measurements of the magnetic susceptibility of LSCO suggest
that the superconducting transition is associated with the disappearance of a
vortex liquid. In this note we wish to draw attention to the fact that
spin-orbit-like interactions in a poorly conducting layered material can lead
to a new type of quantum ground state with spin polarized soliton-like charge
carriers as the important quantum degree of freedom. In 2-dimensions these
solitons are vortex-like, while in 3-dimensional systems they are
monopole-like. In either case there is a natural mechanism for the pairing of
spin up and spin down solitons, and we find that at low temperatures there is a
cross-over transition as a function of carrier density between a state where
the solitons are free and a condensate state where the spin up and spin down
solitons in neighboring layers are paired.Comment: 10 pages, 1 figur
Big Science and the Large Hadron Collider
The Large Hadron Collider (LHC), the particle accelerator operating at CERN,
is probably the most complex and ambitious scientific project ever accomplished
by humanity. The sheer size of the enterprise, in terms of financial and human
resources, naturally raises the question whether society should support such
costly basic-research programs. I address this question here by first reviewing
the process that led to the emergence of Big Science and the role of large
projects in the development of science and technology. I then compare the
methodologies of Small and Big Science, emphasizing their mutual linkage.
Finally, after examining the cost of Big Science projects, I highlight several
general aspects of their beneficial implications for society.Comment: 17 pages; final version to appear in Physics in Perspectiv
Superconductivity Phase Diagram of Na(x)CoO(2).1.3H(2)O
Although the microscopic origin of the superconductivity in high Tc copper
oxides remains the subject of active inquiry, several of their electronic
characteristics are well established as universal to all the known materials,
forming the experimental foundation that all theories must address. The most
fundamental of those characteristics is the dependence of the superconducting
transition temperature on the degree of electronic band filling. Since the
discovery of cuprate superconductivity in 1986 (1), the search for other
families of superconductors that might help shed light on the superconducting
mechanism of the cuprates has been of great interest. The recent report of
superconductivity near 4K in the triangular lattice, layered sodium cobalt
oxyhydrate, Na0.35CoO2.1.3H2O, is the best indication that superconductors
related to the cuprates may be found (2). Here we show that the superconducting
transition temperature of this compound displays the same kind of band-filling
behavior that is observed in the cuprates. Specifically, that the optimal
superconducting Tc occurs in a narrow range of band filling, and decreases for
both underdoped and overdoped materials, in dramatic analogy to the phase
diagram of the cuprate superconductors. Our results suggest that
characterization of the detailed electronic and magnetic behavior of these new
materials may help establish which of the many special characteristics of the
cuprates is fundamental to their high Tc superconductivity.Comment: revised, publication information adde
Accurate theoretical fits to laser ARPES EDCs in the normal phase of cuprate superconductors
Anderson has recently proposed a theory of the strange metal state above Tc
in the high Tc superconductors. [arXiv:cond-mat/0512471] It is based on the
idea that the unusual transport properties and spectral functions are caused by
the strong Mott- Hubbard interactions and can be computed by using the formal
apparatus of Gutzwiller projection. In ref. 1 Anderson computed only the
tunneling spectrum and the power-law exponent of the infrared conductivity. He
had calculated the energy distribution curves (EDCs) in angle resolved
photoemission spectroscopy (ARPES) but was discouraged when these differed
radically from the best ARPES measurements available at the time, and did not
include them. In this letter we compare the spectral functions computed within
this model to the novel laser-ARPES data of the Dessau group.These are found to
capture the shape of the experimental EDCs with unprecedented accuracy and in
principle have only one free parameter
Theory of Structural Glasses and Supercooled Liquids
We review the Random First Order Transition Theory of the glass transition,
emphasizing the experimental tests of the theory. Many distinct phenomena are
quantitatively predicted or explained by the theory, both above and below the
glass transition temperature . These include: the viscosity catastrophe
and heat capacity jump at , and their connection; the non-exponentiality
of relaxations and their correlation with the fragility; dynamic heterogeneity
in supercooled liquids owing to the mosaic structure; deviations from the
Vogel-Fulcher law, connected with strings or fractral cooperative
rearrangements; deviations from the Stokes-Einstein relation close to ;
aging, and its correlation with fragility; the excess density of states at
cryogenic temperatures due to two level tunneling systems and the Boson Peak.Comment: submitted to Ann. Rev. Phys. Che
Quantum dimer models and exotic orders
We discuss how quantum dimer models may be used to provide "proofs of
principle" for the existence of exotic magnetic phases in quantum spin systems.Comment: 12 pages, 6 figures. Contributed talk at the PITP-Les Houches Summer
School on "Quantum Magnetism", June 200
Magnetic Properties of a Superconductor with no Inversion Symmetry
We study the magnetic properties of a superconductor in a crystal without symmetry, in particular how the lack of this symmetry exhibits itself.
We show that, though the penetration depth itself shows no such effect, for
suitable orientation of magnetic field, there is a magnetic field discontinuity
at the interface which shows this absence of symmetry. The magnetic field
profile of a vortex in the plane is shown to be identical to that of an
ordinary anisotropic superconductor except for a shift in the direction by
(see errata). For a vortex along , there is an
induced magnetization along the radial direction.Comment: J. Low Temp. Physics, 140, 67 (2005); with Errat
Randomised, double-blind, placebo controlled study of fluticasone propionate in patients with moderate to severe chronic obstructive pulmonary disease: the ISOLDE trial study
Objectives To determine the effect of long term inhaled corticosteroids on lung function, exacerbations, and health status in patients with moderate to severe chronic obstructive pulmonary disease. Design Double blind, placebo controlled study. Setting Eighteen UK hospitals. Participants 751 men and women aged between 40 and 75 years with mean forced expiratory volume in one second (FEV1) 50% of predicted normal. Interventions Inhaled fluticasone propionate 500 ìg twice daily from a metered dose inhaler or identical placebo. Main outcome measures Efficacy measures: rate of decline in FEV1 after the bronchodilator and in health status, frequency of exacerbations, respiratory withdrawals. Safety measures: morning serum cortisol concentration, incidence of adverse events. Results There was no significant difference in the annual rate of decline in FEV1 (P = 0.16). Mean FEV1 after bronchodilator remained significantly higher throughout the study with fluticasone propionate compared with placebo (P < 0.001). Median exacerbation rate was reduced by 25% from 1.32 a year on placebo to 0.99 a year on with fluticasone propionate (P = 0.026). Health status deteriorated by 3.2 units a year on placebo and 2.0 units a year on fluticasone propionate (P = 0.0043). Withdrawals because of respiratory disease not related to malignancy were higher in the placebo group (25% v19%, P = 0.034). Conclusions Fluticasone propionate 500 ìg twice daily did not affect the rate of decline in FEV1 but did produce a small increase in FEV1. Patients on fluticasone propionate had fewer exacerbations and a slower decline in health status. These improvements in clinical outcomes support the use of this treatment in patients with moderate to severe chronic obstructive pulmonary disease
Algebraic charge liquids
High temperature superconductivity emerges in the cuprate compounds upon
changing the electron density of an insulator in which the electron spins are
antiferromagnetically ordered. A key characteristic of the superconductor is
that electrons can be extracted from them at zero energy only if their momenta
take one of four specific values (the `nodal points'). A central enigma has
been the evolution of the zero energy electrons in the metallic state between
the antiferromagnet and the superconductor, and recent experiments yield
apparently contradictory results. The oscillation of the resistance in this
metal as a function of magnetic field indicate that the zero energy electrons
carry momenta which lie on elliptical `Fermi pockets', while ejection of
electrons by high intensity light indicates that the zero energy electrons have
momenta only along arc-like regions. We present a theory of new states of
matter, which we call `algebraic charge liquids', which arise naturally between
the antiferromagnet and the superconductor, and reconcile these observations.
Our theory also explains a puzzling dependence of the density of
superconducting electrons on the total electron density, and makes a number of
unique predictions for future experiments.Comment: 6+8 pages, 2 figures; (v2) Rewritten for broader accessibility; (v3)
corrected numerical error in Eq. (5
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