92 research outputs found
Quantum mechanical picture of the coupling between interlayer electronic excitations and infrared active phonons in bilayer cuprate superconductors
The formula frequently used to describe the c-axis infrared response of the
coupled electron-phonon system of bilayer cuprate superconductors and providing
important insights into the physics of these materials has been originally
obtained at the level of the phenomenological multilayer model. Here we derive
it using diagrammatic perturbation theory
Selfconsistent gauge-invariant theory of in-plane infrared response of high-Tc cuprate superconductors involving spin fluctuations
We report on results of our theoretical study of the in-plane infrared
conductivity of the high-Tc cuprate superconductors using the model where
charged planar quasiparticles are coupled to spin fluctuations. The
computations include both the renormalization of the quasiparticles and the
corresponding modification of the current-current vertex function (vertex
correction), which ensures gauge invariance of the theory and local charge
conservation in the system. The incorporation of the vertex corrections leads
to an increase of the total intraband optical spectral weight (SW) at finite
frequencies, a SW transfer from far infrared to mid infrared, a significant
reduction of the SW of the superconducting condensate, and an amplification of
characteristic features in the superconducting state spectra of the inverse
scattering rate 1/tau. We also discuss the role of selfconsistency and propose
a new interpretation of a kink occurring in the experimental low temperature
spectra of 1/tau around 1000cm^{-1}.Comment: 9 pages with 6 figures, submitted to Physical Review
Spectroscopic distinction between the normal state pseudogap and the superconducting gap of cuprate high T_{c} superconductors
We report on broad-band infrared ellipsometry measurements of the c-axis
conductivity of underdoped RBa_{2}Cu_{3}O_{7-d} (R=Y, Nd, and La) single
crystals. Our data provide a detailed account of the spectral weight (SW)
redistributions due to the normal state pseudogap (PG) and the superconducting
(SC) gap. They show that these phenomena involve different energy scales,
exhibit distinct doping dependencies and thus are likely of different origin.
In particular, the SW redistribution in the PG state closely resembles the one
of a conventional charge- or spin density wave (CDW or SDW) system.Comment: 4 pages, 4 figure
Extracting the electron--boson spectral function F() from infrared and photoemission data using inverse theory
We present a new method of extracting electron-boson spectral function
F() from infrared and photoemission data. This procedure is
based on inverse theory and will be shown to be superior to previous
techniques. Numerical implementation of the algorithm is presented in detail
and then used to accurately determine the doping and temperature dependence of
the spectral function in several families of high-T superconductors.
Principal limitations of extracting F() from experimental
data will be pointed out. We directly compare the IR and ARPES
F() and discuss the resonance structure in the spectra in
terms of existing theoretical models
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