Anisotropy of the reflectance spectrum and of the dielectric function of YBa2Cu3O7 within the (001) plane

Pb0.4Bi1.6Ma1, Alméras2, Kelley3 et al. 1995Phys. Rev. B

“…[10][11][12] The c−axis resistivity ρ c increases as x increases, and the interlayer coupling weakens. Several reports [13] indicate that the chain electronic states are involved in the superconducting properties.…”

Dipolon-plasmon interaction in high-Tcsuperconducting materials

“…Our calculated value ͑1.15 eV͒ of the plasma frequency agrees with the experimental value observed in various high-temperature superconductors. [2][3][4][5][6][7][8][9][13][14][15][16][17][18] Comparing the slopes of the interacting plasma wave frequency ͑solid line-with interaction-in Fig. 1͒ with the noninteracting plasma wave frequency 1 ͑dashed linewithout interaction-in Fig.…”

“…Furthermore, Koch, Geserich and Wolf 40 have concluded that the 0.58 eV broadband is not due to the interband transitions as the interband transitions require energy greater than 1.7 eV. It is worth remarking that for the broadband 0.58 eV ͑or, in general, 0.5 eV broadband in cuprates͒ referred to above, different interpretations have been proposed by various authors which involve charge transfer or excitonic excitations, 3,4 inelastic-scattering process, 5 valenceconserving dϪd transitions within the e g orbitals of the Cu 2ϩ ͑2͒ ions, 42 localized excitations associated with the b axis Cu-O chains, 43 etc.…”

“…A similar situation exists in other investigations as regards the origin of this peak. [2][3][4][5][6][7][8][13][14][16][17][18] From the detailed form of the observed frequency and temperature dependence of the conductivity in YBa 2 Cu 3 O 7Ϫ␦ Thomas et al 5 have predicted that the electrons interact strongly with some ͑unknown͒ spectrum of excitations to produce this ͑1.1 eV͒ peak. Recently Lee and Sharma 24 have calculated the dispersion relations and density of states in several high-temperature superconductors for the dipolon excitations which are the quantized self-sustained collective oscillations of the crystalfield-generated electronic dipoles of the polarizable ͑oxygen͒ ions and obey Bose statistics.…”

Far-infrared and mid-infrared absorption in (Bi,Pb)-Sr-(Ca,Y)-Cu-O

“…Nevertheless, they have given contradictory results as far as the energy and the attribution of the mid-infrared band are concerned. Indeed, while Rotter et al (24) assign an oscillator peaked at 2000 cm -1 to the Cu-O chains, Koch et al (25) do not find any extra-Drude contribution from the chains for photon frequencies lower than about 8000 crn -1. In turn, the Cu-O planes contribute a Lorentz oscillator at about 4600 cm -1.…”