LONG-WAVELENGTH COLLECTIVE EXCITATIONS OF CHARGE-CARRIERS IN HIGH-TC SUPERCONDUCTORS

[摘要] The long-wavelength dispersion of the charge-carrier plasmon in Bi2Sr2CaCu2O8 for wave vectors parallel to the CuO2 planes has been investigated by transmission-electron energy-loss spectroscopy. For the [100] and the [110] directions the size of the quadratic plasmon dispersion differs by a factor of about 2. This strong in-plane anisotropy can be explained by a calculation in the framework of the random-phase approximation using a simple tight-binding ansatz for the CuO band having a quadratic Fermi surface. However, a different Fermi surface at a lower-energy scale cannot be excluded.

[关键词] ANGLE-RESOLVED PHOTOEMISSION;ELECTRON-ENERGY-LOSS;FERMI-SURFACE;NORMAL-STATE;BI2SR2CACU2O8