1,017 research outputs found
Raman scattering from a superconductivity-induced bound state in
It is shown that the sharp peak in the Raman spectrum of
superconducting is due to a bound state caused by the electron-phonon
coupling. Our theory explains why this peak appears only in the spectra with
symmetry and only in the but not bands. The properties
of the bound state and the Raman spectrum are investigated, also in the
presence of impurity scattering.Comment: 4 pages, 4 figures, will appear in PR
Statistical Analysis of "Structural Change" - An Annotated Bibliography
Within the framework of the Economic Structural Change Program, a cooperative research activity of IIASA and the University of Bonn, FRG, a project is carried out on "Statistical and Econometric Identification of Structural Change"; the project involves studies on the formal aspects of the analysis of structural changes. On the one hand, they include statistical methods to detect non-constancies, such as stability tests, detection criteria, etc., and on the other hand, methods which are suitable for models which incorporate nonconstancy of the parameters, such as estimation techniques for time-varying parameters, adaptive methods, etc.
The present paper provides a documentation of the state of the art in the form of a bibliography
Non-equilibrium dynamics of a system with Quantum Frustration
Using flow equations, equilibrium and non-equilibrium dynamics of a two-level
system are investigated, which couples via non-commuting components to two
independent oscillator baths. In equilibrium the two-level energy splitting is
protected when the TLS is coupled symmetrically to both bath. A critical
asymmetry angle separates the localized from the delocalized phase.
On the other hand, real-time decoherence of a non-equilibrium initial state
is for a generic initial state faster for a coupling to two baths than for a
single bath.Comment: 22 pages, 9 figure
Real Time Evolution in Quantum Many-Body Systems With Unitary Perturbation Theory
We develop a new analytical method for solving real time evolution problems
of quantum many-body systems. Our approach is a direct generalization of the
well-known canonical perturbation theory for classical systems. Similar to
canonical perturbation theory, secular terms are avoided in a systematic
expansion and one obtains stable long-time behavior. These general ideas are
illustrated by applying them to the spin-boson model and studying its
non-equilibrium spin dynamics.Comment: Final version as accepted for publication in Phys. Rev. B (4 pages, 3
figures
Raman-Scattering Detection of Nearly Degenerate -Wave and -Wave Pairing Channels in Iron-Based BaKFeAs and RbFeSe Superconductors
We show that electronic Raman scattering affords a window into the essential
properties of the pairing potential of
iron-based superconductors. In BaKFeAs we observe band
dependent energy gaps along with excitonic Bardasis-Schrieffer modes
characterizing, respectively, the dominant and subdominant pairing channel. The
symmetry of all excitons allows us to identify the subdominant
channel to originate from the interaction between the electron bands.
Consequently, the dominant channel driving superconductivity results from the
interaction between the electron and hole bands and has the full lattice
symmetry. The results in RbFeSe along with earlier ones in
Ba(FeCo)As highlight the influence of the Fermi
surface topology on the pairing interactions.Comment: 5 pages, 4 figure
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