銅氧化物超導體Tc與銅氧面電洞之研究

Abstract

我們利用同步輻射高度極化的光源，進行O 1s和 Cu 2p近吸收邊緣X光吸收光譜實驗，探測Y1-xCaxBa2Cu3O6+y (x=0、0.3, 0≦y≦1)薄膜的銅氧平面費米能階附近電子組態。來了解各異向性載子在釔鋇銅氧化物超導機制中扮演什麼角色。 除了從實驗數據探討各異向性載子與Tc的關係，本論文還探討摻鈣的機制，並與M. Merz et al. (Phys. Rev. Lett. 80, 5192 (1998))、M. Karppinen et al. (J. Solid state Chem. 166, 229 (2002)) 等人光譜實驗結論作比較，並討論實驗爭議的地方。 我們的結論是銅氧平面的載子數決定了釔鋇銅氧化物高溫超導性。銅氧化物超導體Tc與軸向氧上載子無關。

Using polarized soft x-ray from synchrotron radiation, the site-specific electronic structures of Y1-xCaxBa2Cu3O6+y (x=0, 0.3, 0≦y≦1) have been investigated by O 1s and Cu 2p near edge x-ray absorption spectroscopy. We obtain information about the hole concentration on specific sites. The main issue of this thesis is to understand the roles of the hole carriers on specific sites in Y1-xCaxBa2Cu3O6+y , especially their effects on Tc . The mechanism of Ca doping on Y1-xCaxBa2Cu3O6+y will also be discussed in this thesis. Furthermore the results will be compared to those of Merz et al. (Phys. Rev. Lett. 80, 5192 (1998)) and M. Karppinen et al. (J. Solid state Chem. 166, 229 (2002)) to discuss some controversial issues. It is concluded that the number of the planar holes plays the major role on determining Tc of Y1-xCaxBa2Cu3O6+y. The holes of the apical sites are not important to Tc in Y1-xCaxBa2Cu3O6+y at all.