低維度材料在理論及實驗方面已經被廣泛的研究。在石墨烯與過渡金屬二硫屬化物等二維材料中的磁性研究正迅速的成長。在材料中透過邊界、原子空缺、晶界等晶體缺陷所創造的磁性為數據儲存與磁性感應等領域帶來革命性的變化。 在本論文中，我們以密度泛函理論為基礎的第一原理計算研究二硒化鉑鋸齒狀奈米帶的電子特性及磁性。奈米帶的內部為非磁性的半導體，磁性則由分布在 鋸齒狀邊界的一維磁通道及金屬通道所主導，其中鉑 d 軌道與硒 p 軌道之耦合則扮演重要的角色。針對垂直於邊界壓縮所引發的磁性到非磁性的轉變，我們延伸安德森雜質模型並透過參數擬合發現：以邊界上金屬通道作為媒介，磁性通道的交換分裂隨著結構改變而縮小直至磁性的消失。相較於二硒化鉑，二硒化鉿鋸齒狀奈米帶的磁性並不會隨著結構拉伸或壓縮而有明顯改變。此截然不同的結果為顯著的離子鍵特性與低佔據比例的鉿 d 軌道所導致。這些發現說明過渡金屬在一維磁性過渡金屬二硫屬化物的重要角色。二硒化鉑的獨特性使其極具潛力成為自旋電子元件中能有效開關的重要材料。;Low-dimensional material has been a long-time subject of both theoretical and experimental aspects. Beyond the intrinsic magnetic solids, searching for magnetism in graphene, transition metal dichalcogenides (TMDs), and other two-dimensional materials has continued apace. Realized either by introducing edges, vacancies, or grain boundaries, magnetism in defect-engineered materials has revolutionized important technologies such as data storage and magnetic sensing. Here the density functional theory (DFT) calculations are employed to investigate the electronic properties and the sizable magnetization in zigzag-edged PtSe2 (zz-PtSe2) nanoribbon. Quasi one-dimensional magnetic and metallic channels are found at two edges of the nanoribbon, which are well separated by nonmagnetic and semiconducting states at inner atoms. We discover that the underlying mechanism is the orbital hybridization between edge Pt-d and Se-p orbitals along the edges. Remarkably, our first-principles calculations reveal that the zz-PtSe2 nanoribbon undergoes a magnetic-nonmagnetic transition induced by a compressive strain about -2% perpendicular to the zigzag edges. By fitting the DFT results, the model simulation based on the extension of Anderson’s single impurity model suggests that the change of the edge structures are responsible for the sudden disappearance of the magnetization. The observed magnetic switching originates from the reduction in the exchange splitting of the localized magnetic channels along the edges mediated by metallic backgrounds. In sharp contrast, the magnetization of the zigzag-edged HfSe2 nanoribbon is well preserved under strain, as a consequence of the robust ionicity Hf-Se bond and the low d-band occupancy of the edge Hf. Such finding highlights the role of the transition metal in TMD-based one-dimensional magnets. The uniqueness of PtSe2 provides a promising direction for effective mechanical switching and further application in spintronics devices.
