Symmetry dependence of phonon lineshapes in superconductors with anisotropic gaps

The temperature dependence below $T_{c}$ of the lineshape of optical phonons of different symmetry as seen in Raman scattering is investigated for superconductors with anisotropic energy gaps. It is shown that the symmetry of the electron-phonon vertex produces non-trivial couplings to an anisotropic energy gap which leads to unique changes in the phonon lineshape for phonons of different symmetry. The phonon lineshape is calculated in detail for $B_{1g}$ and $A_{1g}$ phonons in a superconductor with $d_{x^{2}-y^{2}}$ pairing symmetry. The role of satellite peaks generated by the electron-phonon coupling are also addressed. The theory accounts for the substantial phonon narrowing of the $B_{1g}$ phonon, while narrowing of the $A_{1g}$ phonon which is indistinguishable from the normal state is shown, in agreement with recent measurements on BSCCO.Comment: 15 pages (3 Figures available upon request), Revtex, 1

A Consistent Picture of Electronic Raman Scattering and Infrared Conductivity in the Cuprates

Calculations are presented for electronic Raman scattering and infrared conductivity in a $d_{x^{2}-y^{2}}$ superconductor including the effects of elastic scattering via anisotropic impurities and inelastic spin-fluctuation scattering. A consistent description of experiments on optimally doped Bi-2212 is made possible by considering the effects of correlations on both inelastic and elastic scattering.Comment: 4 pages Revtex, 5 embedded eps file

Neutron Scattering and the B_{1g} Phonon in the Cuprates

The momentum dependent lineshape of the out-of-phase oxygen vibration as measured in recent neutron scattering measurements is investigated. Starting from a microscopic coupling of the phonon vibration to a local crystal field, the phonon lineshift and broadening is calculated as a function of transfered momentum in the superconducting state of YBa$_{2}$Cu$_{3}$O$_{7}$. It is shown that the anisotropy of the density of states, superconducting energy gap, and the electron-phonon coupling are all crucial in order to explain these experiments.Comment: new figures and discussio

The Pairing Mechanism in HTSC investigated by Electronic Raman Scattering

By means of electronic Raman scattering we investigated the symmetry of the energy gap Delta(k), its temperature dependence and its variation with doping of well characterized Bi2Sr2CaCu2O8+delta single crystals. The oxygen content delta was varied between the under- and the overdoped regime by subsequently annealing the same single crystal in Ar and O2, respectively. The symmetry analysis of the polarized electronic Raman scattering is consistent with a d_x^2-y^2-wave symmetry of the energy gap in both regimes. The gap ratio 2Delta_max/k_BT_c and its temperature dependence changes with doping similar to predictions of theories based on paramagnon coupling.Comment: 3 pages, LaTeX, 2 ps figures available on request to [email protected]

Flight test investigation of the vortex wake characteristics behind a Boeing 727 during two-segment and normal ILS approaches (A joint NASA/FAA report)

Flight tests were performed to evaluate the vortex wake characteristics of a Boeing 727 aircraft during conventional and two-segment instrument landing approaches. Smoke generators were used for vortex marking. The vortex was intentionally intercepted by a Lear Jet and a Piper Comanche aircraft. The vortex location during landing approach was measured using a system of phototheodolites. The tests showed that at a given separation distance there are no readily apparent differences in the upsets resulting from deliberate vortex encounters during the two types of approaches. The effect of the aircraft configuration on the extent and severity of the vortices is discussed

Enhanced Electron-Phonon Coupling and its Irrelevance to High Tc_{c} Superconductivity

It is argued that the origin of the buckling of the CuO$_{2}$ planes in certain cuprates as well as the strong electron-phonon coupling of the $B_{1g}$ phonon is due to the electric field across the planes induced by atoms with different valence above and below. The magnitude of the electric field is deduced from new Raman results on YBa$_{2}$Cu$_{3}$O$_{6+x}$ and Bi$_{2}$Sr$_{2}$(Ca$_{1-x}$Y$_{x}$)Cu$_{2}$O$_{8}$ with different O and Y doping, respectively. In the latter case it is shown that the symmetry breaking by replacing Ca partially by Y enhances the coupling by an order of magnitude, while the superconducting $T_c$ drops to about two third of its original value.Comment: 4 pages, 2 figures. This and other papers can be downloaded from http://gwis2.circ.gwu.edu/~tp

Relation between the superconducting gap energy and the two-magnon Raman peak energy in Bi2Sr2Ca{1-x}YxCu2O{8+\delta}

The relation between the electronic excitation and the magnetic excitation for the superconductivity in Bi2Sr2Ca{1-x}YxCu2O{8+\delta} was investigated by wide-energy Raman spectroscopy. In the underdoping region the B1g scattering intensity is depleted below the two-magnon peak energy due to the "hot spots" effects. The depleted region decreases according to the decrease of the two-magnon peak energy, as the carrier concentration ncreases. This two-magnon peak energy also determines the B1g superconducting gap energy as $2\Delta \approx \alpha \hbar \omega_{\rm Two-Magnon} \approx J_{\rm effective}$ $(\alpha=0.34-0.41)$ from under to overdoping hole concentration.Comment: 10 pages, 4 figure

Reply to Comment on:"Nonmonotonic d_{x^2-y^2} Superconducting Order Parameter in Nd_{2-x}Ce_xCuO_4"

We confirm that all the results of scanning SQUID, tunneling, ARPES, penetration depth and Raman experiments are consistent with a nonmonotonic d_{x^2-y^2} superconducting order parameter proposed in Phys. Rev. Lett., 88, 107002 (2002).Comment: Reply to Comment by F. Venturini, R. Hackl, and U. Michelucci cond-mat/020541