[[alternative]]Effects of Local Lattice Distortion, Structural Phase Transition and Doping-Induced Disorder on Physical Properties of Transition-Metal Oxide Superconductors

計畫編號：NSC99-2112-M032-004-MY3 研究期間：201008~201107 研究經費：1,701,000[[abstract]]本計畫的研究目標是探討局部晶格扭曲、結構相變以及參雜誘發的無序與稀釋效應對新穎過渡金屬氧化物超導體物理性質的影響，主要研究的系統為 (1) 超導弱鐵磁石RuSr2RCu2O8 (R = Gd, Eu)，(2) 鹼金屬鎢青銅礦AxWO3+δ (A =鹼金屬)，(3) 非晶質 (In2O3)1-x-ZnOx(00.03)x≤≤薄膜。預期將對過渡金屬氧化物超導性產生的機制有較完整的理解，裨益於未來新超導材料的探尋。對於超導弱鐵磁石系統，我們將在銅氧平面上作磁性(Ni)/非磁性(Zn)原子的參雜，來調制銅3d軌道上電子自旋的擾動與釕氧平面上的G-型傾斜反鐵磁序，研究超導與磁序的關聯性。對於鹼金屬鎢青銅礦，我們將改變氧含量、參雜少量的Mo/Nb原子於W的位置、成長薄膜樣品於晶格常數不匹配的基板上，利用應力效應來調變WO6八面體的扭曲程度或產生可能的結構相變，研究超導性與電荷密度波共存的相依性。對於非晶質銦鋅氧化物薄膜，我們將改變薄膜的成長條件與厚度來調變無序的程度、改變退火條件來調制載子的濃度，或參雜磁性雜質來抑制低溫下傳導電子間的量子干涉現象(弱局域性)，有系統地探究此非晶質薄膜中存在的無序引致超導-絕緣體轉變。[[abstract]]We propose to investigate the effects of local lattice distortion, phase transition and doping-induced disorder on physical properties of transition-metal-oxide (TMO) superconductors. The systems we’re going to study are (1) superconducting weak ferromagnets RuSr2RCu2O8 (R = Gd, Eu), (2) alkali- metal tungsten bronzes AxWO3+δ (A = alkali metals), (3) amorphous (In2O3)1-x-ZnOxwith 00.03x≤≤ thin films. This proposal aims to have a comprehensive understanding on underlying mechanism of superconductivity in TMOs and expects to provide a clue for searching new classes of superconducting materials in the near future. We plan to study how the superconducting CuO2 bilayer couping propagates through the magnetic RuO2 layers by partially substituting Cu in RuSr2RCu2O8 with nonmagnetic Zn or magnetic Ni atom. Secondly, an attempt to be made to elucidate the interplay between superconductivity and charge density wave in alkali-metal tungsten bronzes AxWO3+δ by varying oxygen content, doping Mo/Nb at W site, and depositing films on lattice-mismatch substrates to modify the lattice distortion of WO6 octahedra and possibly induce phase transition as well. Finally, we intend to systematically study the disorder-tuned superconductor-insulator transition in amorphous (In2O3)1-x-ZnOx thin films by adjusting a number of parameters including film thickness, annealing condition, magnetic field, and carrier concentration.[[sponsorship]]行政院國家科學委員