探討拓撲半金屬之量子振盪效應

Investigation of Quantum Oscillation Effects in Topological Semimetals

林芝羽(Chih-Yu Lin)

指導教授 ： 郭光宇

共同指導教授 ： 李偉立(Wei-Li Lee)

國立臺灣大學/理學院/物理學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102280

摘要

拓撲半金屬系統是近年來固態物理領域重要的議題之一，許多的理論預測了新興的拓撲態，其中部分的性質被實驗證實，仍有很多的拓撲態性質等待被發掘。在本論文中，我們藉由磁電性量測以及磁矩量測來探討Weyl半金屬SrRuO3、狄拉克節線系統SrAs3以及反鐵磁材料GdSb0.5Te1.5中可能存在的拓撲節線半金屬態。在SrRuO3薄膜的量子振盪中，我們在30特斯拉的頻率中發現了罕見的大幅度量子振盪相位移，此現象與Weyl半金屬獨特的費米弧表面態有直接的關聯。從單晶的SrAs3系統量子震盪分析中，發現存在極小的費米面，進而以在僅僅約1.5特斯拉的磁場強度下，進入量子極限範疇。在GdSb0.5Te1.5的磁性量測中，我們發現磁性隨磁場大小而有豐富的轉變，顯示此系統中複雜而有趣的電磁效應。這些拓撲材料與特殊的拓撲表面電子態，大幅增加了未來量子電子元件的可能性。

關鍵字

拓撲半金屬 ； Weyl半金屬 ； 拓撲節線半金屬態 ； 量子振盪 ； SrRuO3 ； SrAs3 ； GdSb0.5Te1.5

並列摘要

Topological semimetal is a rapidly rising star of condensed-matter physics and material science. It has been predicted that many exotic phases of matter exist in topological semimetals, and some of the properties were confirmed by experiments. However, there are still a number of topological phases unknown and uninvestigated. Here, we report the magnetotransport and magnetization measurements of the Weyl semimetal SrRuO3, topological nodal line semimetal SrAs3, and antiferromagnetic material GdSb0.5Te1.5. In SrRuO3 thin films, we observed an unusual large phase shift in the quantum oscillation at a frequency of 30 T associated with the Fermi arc surface states in the Weyl semimetal. In the single crystal SrAs3, the quantum oscillation with a frequency of 1.5 T indicates an extremely small Fermi surface. Moreover, we reach the quantum limit of about 1.5 T. In the magnetization measurement of antiferromagnetic material GdSb0.5Te1.5, the phase transitions due to the change of the magnetic field reveal a complex galvanomagnetic effect. These topological materials and exotic topological surface states could be useful to technological applications and open new possibilities for spintronics and quantum computing.

並列關鍵字

Topological semimetal ； Weyl semimetal ； Topological nodal line semimetal ； Quantum oscillation ； SrRuO3 ； SrAs3 ； GdSb0.5Te1.5

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