Plasmons in high-temperature superconductors

✍ Scribed by J.H. Kim; I. Bozovic; J.S. Harris Jr.; W.Y. Lee; C.B. Eom; T.H. Geballe; E.S. Hellman

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 174 KB
• Volume: 185-189
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(91)91733-k

✦ Synopsis

Plasmon spectra of Dee carriers in high-T¢ cuprates and bismates are investigated via their complex dielectric functions, which are accurately determined by combining reflectance and spectrodlipsometric measurements. All five superconductors under study exhibit a single optic plasmon located at 0.8 eV for LaLssSroasCuO4, 1.4 eV for YBa2CuaOr, 1.0 eV for Bi~Sr~CaCuzOs, 1.2 eV for 'Fl~Ba~CazCuaOm, and 1.5 eV for Bao.s4K0.~sBiOa. The low-energy part of the dielectric loss function of each system is quadratic with frequency: Im(-1/¢) = flw 2, nearly up to the screened plasma frequency. We propose that this characteristic quadratic frequency dependence is universally obeyed in all high-T¢ superconductors.

Reliable information on the relevant low-energy electronic excitations is essential to clarify the mechanism of high-T~ superconductivity. Optical spectroscopy is generally a useful source of such information) In particular, study of plasmons not only helps understand their possible role in the pairing interaction3 -6 but also provides