2023-01-012024-05-16https://scholars.lib.ntu.edu.tw/handle/123456789/669694在超導物理領域中，沿著c 軸探討超導體不同原子層之間的交互作用之關係，探索不同面向的超導特質之完整性，一直以來是實驗超導物理領域未實現之目標。然而，依目前科技發展看來，剖面掃描穿隧顯微鏡似乎是唯一能實現這個研究目標的量測儀器。 申請人過去10年皆在發展以及利用剖面掃描穿隧顯微鏡量測尖端新穎材料系統。材料含括有半導體、複合氧化物、有機能源材料之剖面物性、異質界面特質。本研究計畫，擬依10多年之研究經驗，利用剖面掃描穿隧顯微鏡探討超導物理領域中，一直未成功探索的沿著c 軸之超導物理：利用剖面探討超導體原子層之間交互作用關係、異質界面處之鄰近效應，以及超導體內實空間直接微觀競爭相圖。 本三年計畫中，擬探討研究主題說明如下： 1) [超導異質結構之界面耦合] 首先、擬探討研究主題為超導異質物質界面處的鄰近效應(proximity effect)。所謂的鄰近效應是指超導物質和金屬之間的接合面處，電子結合在一起的庫柏電子對(cooper pairs)會在接合面處發生削弱(超導物質) 亦或是引進(金屬) 的現象。因此，鄰近效應相關的物理機制被視為在未來電子元件中，可被應用操控界面處超導特質之調控方法。然而，截至目前為止，一直尚未有直接量測的實驗進而探討相關物理機制。 2) [超導微觀競爭相圖] 第二、高溫超導被發現已有30多年的時間。然而，由於超導物質的氧缺不均勻性以及物理機制之複雜性，微觀的相圖仍是不足的。其中，最為不足的相圖乃屬高溫超導體的代表性材料，釔鋇銅氧超導(YBa2Cu3O6+x)。其中，最嚴重未被了解的科學實驗是在於釔鋇銅氧超導物質內，電荷有序態(Charge Order)和超導(Superconductivity)實空間之微觀競爭相圖。 3) [超導原子層之間的交互作用] 第三、擬探討研究主題為釔鋇銅氧超導(YBa2Cu3O6+x)物質內，未被釐清的銅氧鍊(CuO chains)在超導電荷有序態(Charge Order)中，所扮演的角色。銅氧鍊(CuO chains)所扮演的角色之所以尚未在超導領域被釐清的主要原因在於釔鋇銅氧超導體，最易被取得的表面為銅氧面(CuO2planes) 以及鋇氧面(BaO planes)。因此，欲釐清銅氧鍊在超導電荷有序態所扮演的角色，取得剖面沿著c軸量測銅氧鍊之電子結構，是唯一目前可以探討相關物理機制的實驗方法。因此，實驗必須突破二個關鍵技術：(i) 如何在實驗上，取得釔鋇銅氧超導(YBa2Cu3O6+x) 的剖面結構影像。(ii) 如何在實驗上，利用剖面，量測原子級的電子結構特質。唯有取得剖面結構影像，並量測原子級的電子結構特質，超導原子層之間的交互作用以及銅氧鍊在電荷有序態中的角色，才能釐清。 本研究計畫的成果，預期提供超導領域第一手實空間並有沿著超導物質c 軸剖面結構的原子影像，以及原子級的電性結果。這份實驗結果，預期開闊對超導物理有嶄新不同材料面向物理機制的了解和未來科技之應用。 To obtain atomically resolved electronic results of cross-sectionally cleaved superconductor-based heterostructures to explore the superconductivity physics along the c [001] direction across the different atomic layers has been a long-term goal in the physics community more than 30 years. The dream goal is only achievable thus far by using cross-sectional scanning tunneling microscopy (XSTM). In the past more than 10 years, the PIinvested efforts to obtain the direct real-space XSTM results from the cross-sectionally cleaved side, including semiconductor-based interfaces, oxide interfaces, and organic-based interfaces. Based on the experience, in the current proposal, the PI proposes to utilize the XSTM/S technique to explore the unknown superconductivity physics along the c [001] direction across the different atomic layers. To explore the unknownsuperconductivity physics along the c [001] direction in superconductor-based systems is the main aim in this proposal. Three critical topics to be discussed in this three-year proposal: 1) [Interface coupling at cuprate/substrate interfaces] The first topic is to discuss the proximity effect (PE). The proximity effect, occurring at the interface between superconductor and metal, wherein the superconducting pairs can penetrate into the metal. This leads to a possible manipulation of the reduction in superconductivity and the introduction of superconducting order parameter at the superconductor-based interfaces. Hence, to explore the nature of the proximity effect becomes not only a promising route to manipulate the superconductivity, but also in the development of future oxide-based electronic devices. 2) [Competing ordersin cupartes] The second one is to discuss the phase competition in high-temperature superconductivity cuprates. High-temperature superconductors have been discovered for more than30 years. However, due to their intrinsic inhomogeneity and the complex phase diagram, a widely accepted microscopic picture is still missing. For example, YBa2Cu3O6+x acts as a benchmark high-temperature superconductor. However, although charge-ordering (CO) was identified as a key factor in competition with superconductivity in cuprate superconductors, a spatially-resolved technique capable of direct access to the CO regime is still lacking. 3) [Interlayer coupling in cupartes] The third one is to discuss the unknown role of CuO-chainlayersin the formation of charge density waves (CDW) in high-temperature superconductivity cuprates. CDW order on CuO2planewas revealed in X-ray experiments to exhibit its distinct directionality depending on the oxygen content. However, whether the CDW order on CuO2plane and CuO chain layer is independent of one another or there is correlation across layers still is an unclear question. To discuss the above critical issues in superconductivity, XSTM experiments need to make the breakthrough to achieve imaging with atomic resolution and to characterize the atomically resolved electronic structure along the c [001] direction in high-temperature superconductive cuprates. The achievements of the proposal will be the first direct real-space evidence with atomically resolved electronic results along the c [001] direction in superconductivity. In addition, the completion of the proposal will therefore demonstrate a new approach to unravel fundamental mechanisms of superconductivity in physics community.剖面掃描穿隧顯微鏡超導物理;鄰近效應電荷有序態原子級電子結構;cross-sectional scanning tunneling microscopy (XSTM); superconductivity; charge ordering; proximity effect; atomically resolved electronic structure