材料的形變工程顯著改變了石墨烯的電子特性。形變工程可以使石墨烯的晶格結構產生彎曲、變形，進而影響電子的傳輸方式。有研究表明，形變工程可以在石墨烯內誘發高達數百特斯拉的偽磁場，生成具有電子強關連性質的電子平帶結構，甚至實現超導。形變工程在純粹由碳原子組成的石墨烯電子傳輸特性上的操縱對由強關聯電子系統誘發的量子現象研究上展現了巨大潛力。要推動這一領域的發展，形變工程的成熟和精確控制至關重要。然而現有的形變工程技術還無法精準地控制形變在材料上的分佈，局域的形變工程也還無法達到奈米級的精準度，有些方法誘發的材料形變甚至會隨著時間還有溫度退化。我們的團隊開發了一套精湛的形變工程技術，可以在石墨烯上精確地建構出具週期性排列的材料形變，其在材料上誘發的形變具有高度可控性和優異的均勻性，我們稱其為『形變超晶格』。我們已經成功地在一維形變的波紋排列超晶格雙層石墨烯和二維形變的六方排列超晶格形變三層石墨烯中根據其各自不同的形變超晶格排列設計而實現了不同的量子特性。為了揭開電子的強關聯作用與不同形變超晶格排列之間的面紗以了解他們之間如何微妙的耦合，我設計了另一個不同的形變超晶格排列－『正方排列超晶格形變三層石墨烯』。我的研究結果顯示形變超晶格在雙層石墨烯內增強了電子之間的相互耦合。電子的運輸特性在5K以上以下的溫度區間分別受兩種不同的機制主導。在5K以下的極低溫環境中，我們觀察到庫倫能隙的出現，並且電子的傳輸主要由『Efros-Shklovskii變程跳躍模型』來描述。而在5K以上，電子的行為類似於傳統半導體，可以藉由『Arrhenius傳輸模型』所描述，表現出像是彼此間沒有交互作用的費米子一樣。再者，我們還觀察到電子導電性對溫度和施加電流呈現一個常在強相關電子系統出現的冪次關係，暗示我們的系統擁有強關聯電子特性。此外，我們在六方排列超晶格形變三層石墨烯中觀察到的幾何挫折的反鐵磁有序態僅能夠在六方形變超晶格中實現。這讓我們得出一個重要的結論，電子之間的強關聯作用型態是由形變超晶格的排列設計所決定的。

Strain engineering in graphene significantly modifies its electronic properties. Strain deforms its lattice structure and deflects the electron transport. It has been reported that strain can induce a pseudo-magnetic field up to few hundred tesla, generate a electronic flat band, and achieve superconducting. This technique holds great promise for exploring fascinating quantum phenomena in strongly correlated electron systems within a purely carbon-based platform. Proficient and precise control of strain is key to advance. However, common methods to induce strain are often randomly distributed, lack nano-scale precision, and may relax over time. Our team has developed a talented method to fabricate periodic strain in graphene, which we called strain-superlattice, with high controllability and excellent uniformity. We successfully realized different emergent quantum phases in a one-dimensional corrugated bilayer graphene and a two-dimensional hexagonal-superlattice-strained-trilayer graphene according to their different configuration in strain arrangement. To unveil the hidden parameter in the interplay between electron correlation and strained-superlattice, I turned to a square-superlattice-strained-bilayer graphene. The transport properties of the electrons are observed to be dominated by two different mechanisms, with a transition occurring at 5K. A pronounced Coulomb gap described by Efros-Shklovskii variable-range hopping model emerges below 5K, whereas the electrons behave as a conventional semiconductor above 5K, which is characterized by the non-interacting Fermions as described by Arrhenius model. Furthermore, a power law dependence of electron conductance on temperature and source-drain bias is observed, suggesting a strongly correlated electron system. Additionally, we conclude that the emergence of a geometrically frustrated antiferromagnetic ordered state is only realized in the hexagonal-strained superlattice, and the electron-correlated phases created by the strain-superlattice are determined by the arrangement of the strain superlattice.

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