189 research outputs found
Doping-dependent nodal Fermi velocity in Bi-2212 revealed by high-resolution ARPES
The improved resolution of laser-based angle-resolved photoemission
spectroscopy (ARPES) allows reliable access to fine structures in the spectrum.
We present a systematic, doping-dependent study of a recently discovered
low-energy kink in the nodal dispersion of Bi2Sr2CaCu2O8+d (Bi-2212), which
demonstrates the ubiquity and robustness of this kink in underdoped Bi-2212.
The renormalization of the nodal velocity due to this kink becomes stronger
with underdoping, revealing that the nodal Fermi velocity is non-universal, in
contrast to assumed phenomenology. This is used together with laser-ARPES
measurements of the gap velocity, v2, to resolve discrepancies with thermal
conductivity measurements.Comment: Submitted to Phys. Rev. Let
SINGULAR PERTURBATIONS AND BOUNDARY LAYER THEORY FOR CONVECTION-DIFFUSION EQUATIONS IN A CIRCLE: THE GENERIC NONCOMPATIBLE CASE
We study the boundary layers and singularities generated by a convection-diffusion equation in a circle with noncompatible data. More precisely, the boundary of the circle has two characteristic points where the boundary conditions and the external data are not compatible. Very complex singular behaviors are observed, and we analyze them systematically for highly noncompatible data. The problem studied here is a simplified model for problems of major importance in fluid mechanics and thermohydraulics and in physics.open4
Dynamics of Open Bosonic Quantum Systems in Coherent State Representation
We consider the problem of decoherence and relaxation of open bosonic quantum
systems from a perspective alternative to the standard master equation or
quantum trajectories approaches. Our method is based on the dynamics of
expectation values of observables evaluated in a coherent state representation.
We examine a model of a quantum nonlinear oscillator with a density-density
interaction with a collection of environmental oscillators at finite
temperature. We derive the exact solution for dynamics of observables and
demonstrate a consistent perturbation approach.Comment: 7 page
On the flow map for 2D Euler equations with unbounded vorticity
In Part I, we construct a class of examples of initial velocities for which
the unique solution to the Euler equations in the plane has an associated flow
map that lies in no Holder space of positive exponent for any positive time. In
Part II, we explore inverse problems that arise in attempting to construct an
example of an initial velocity producing an arbitrarily poor modulus of
continuity of the flow map.Comment: http://iopscience.iop.org/0951-7715/24/9/013/ for published versio
Phase competition in trisected superconducting dome
A detailed phenomenology of low energy excitations is a crucial starting
point for microscopic understanding of complex materials such as the cuprate
high temperature superconductors. Because of its unique momentum-space
discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally
suited for this task in the cuprates where emergent phases, particularly
superconductivity and the pseudogap, have anisotropic gap structure in momentum
space. We present a comprehensive doping-and-temperature dependence ARPES study
of spectral gaps in BiSrCaCuO (Bi-2212), covering much
of the superconducting portion of the phase diagram. In the ground state,
abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for
two potential quantum critical points, p0.19 for the pseudogap phase and
p0.076 for another competing phase. Temperature dependence reveals that the
pseudogap is not static below T and exists p0.19 at higher temperatures.
Our data imply a revised phase diagram which reconciles conflicting reports
about the endpoint of the pseudogap in the literature, incorporates phase
competition between the superconducting gap and pseudogap, and highlights
distinct physics at the edge of the superconducting dome.Comment: to appear in PNA
Generation of small-scale structures in the developed turbulence
The Navier-Stokes equation for incompressible liquid is considered in the
limit of infinitely large Reynolds number. It is assumed that the flow
instability leads to generation of steady-state large-scale pulsations. The
excitation and evolution of the small-scale turbulence is investigated. It is
shown that the developed small-scale pulsations are intermittent. The maximal
amplitude of the vorticity fluctuations is reached along the vortex filaments.
Basing on the obtained solution, the pair correlation function in the limit
is calculated. It is shown that the function obeys the Kolmogorov law
.Comment: 18 page
Linear instability criteria for ideal fluid flows subject to two subclasses of perturbations
In this paper we examine the linear stability of equilibrium solutions to
incompressible Euler's equation in 2- and 3-dimensions. The space of
perturbations is split into two classes - those that preserve the topology of
vortex lines and those in the corresponding factor space. This classification
of perturbations arises naturally from the geometric structure of
hydrodynamics; our first class of perturbations is the tangent space to the
co-adjoint orbit. Instability criteria for equilibrium solutions are
established in the form of lower bounds for the essential spectral radius of
the linear evolution operator restricted to each class of perturbation.Comment: 29 page
Complex spectral evolution in a BCS superconductor, ZrB12
We investigate the electronic structure of a complex conventional superconductor, ZrB12 employing high resolution photoemission spectroscopy and ab initio band structure calculations. The experimental valence band spectra could be described reasonably well within the local density approximation. Energy bands close to the Fermi level possess t2g symmetry and the Fermi level is found to be in the proximity of quantum fluctuation regime. The spectral lineshape in the high resolution spectra is complex exhibiting signature of a deviation from Fermi liquid behavior. A dip at the Fermi level emerges above the superconducting transition temperature that gradually grows with the decrease in temperature. The spectral simulation of the dip and spectral lineshape based on a phenomenological self energy suggests finite electron pair lifetime and a pseudogap above the superconducting transition temperature
Recommended from our members
Topological surface states above the Fermi level in Hf2Te2 P
We report a detailed experimental study of the band structure of the recently discovered topological material Hf2Te2P. Using the combination of scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy with surface K doping, we probe the band structure of Hf2Te2P with energy and momentum resolution above the Fermi level. Our experiments show the presence of multiple surface states with a linear Dirac-like dispersion, consistent with the predictions from previously reported band-structure calculations. In particular, scanning tunneling spectroscopy measurements provide experimental evidence for the strong topological surface state predicted at 460meV, which stems from the band inversion between Hf-d and Te-p orbitals. This band inversion comprised of more localized d states could result in a better surface-to-bulk conductance ratio relative to more traditional topological insulators
- …