新穎量子物質之物理特性研究,-子計畫一：新穎量子物質之界面及其物理特性研究

Abstract

本計畫主要延續本研究群多年來在鈣鈦礦結構的氧化物薄膜研 究成果，並利用已架設完成的薄膜製程機台與低溫量測系統來探討新 穎量子物質界面之物理特性。我們將利用脈衝雷射搭配既有的雷射分 子磊晶成長系統（Laser MBE System），製備各種不同軸向的多鐵錳 氧化物薄膜和奈米顆粒，並利用XRD、AFM 等量測系統得知晶體結 構、表面平整度與電性，檢驗多鐵錳氧化物的一般物理特性。接著在 成長有不同軸向的多鐵錳氧化物薄膜和奈米顆粒的基板上，成長高溫 超導或拓樸絕緣體薄膜，形成異質量子物質之接面結構。希望藉由調 變多鐵薄膜的反鐵磁性，以及其衍生的鐵電特性，觀察其對超導臨界 電流與臨界溫度變化的影響。尤其是低溫時E-type 之反鐵磁相變溫 度，是否也會相對的受到超導特性影響而產生變化。本計畫亦擬研究 (Bi1-xSbx)2(Te1-ySey)3 材料系統，針對不同摻雜濃度所造成量測之NMR 頻譜的變化，並利用奈特位移觀察其表面的缺陷。這些結果將與利用 ARPES 觀察到的能帶結構比較，以了解拓墣絕緣體的特性。

This proposal is mainly an extension of the efforts that our group had put forth in investigating perovskite oxides thin films over the past decade. We will further our efforts to investigate the physical properties of the interfaces formed between the novel quantum matters by using the film preparation and characterization facilities established. We will combine the PLD system with the laser MBE system to prepare multiferroic films with distinct crystallographic orientations as well as nanostructures of the same materials. The general physical properties such as crystal structure, surface morphology, and multiferroics characteristic will be checked by XRD、AFM and transport measurement systems. Subsequently, we will deposit other quantum matters, such as high-Tc superconducting thin films and newly discovered topological insulators, onto substrates grown with the abovementioned multiferroic films or nanostructures. It is anticipated that by modulating the antiferromagnetic phase and the associated ferroelectricity, the superconducting properties will be modulated. In particular, it will be interesting to observe whether the multiferroicity will be changed by the proximity of superconductivities. We will also put some efforts on studying the (Bi1-xSbx)2(Te1-ySey)3 topological insulator systems by using NMR techniques. In particular, we will study the spectrum change as well as the Knight shift as a function of doping concentration variation to delineate the effects of impurity on the surface conducting states. These results will be compared with the corresponding band structure results from the ARPES measurements performed by our collaborators to shed some lights on these novel quantum matters.