鐵插層碲化鉍單晶之電磁傳輸特性研究

Magnetotransport properties of Fe-intercalated topological insulator(Bi2Te3) single crystal

王碩宏(Shuo-Hong Wang)

指導教授 ： 王立民

國立臺灣大學/理學院/物理學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903352

摘要

近體拓撲材料引發許多關注，如以具有狄拉克錐表面態的拓撲絕緣體(TI)材料Bi2Se3及Bi2Te3被用於近期熱門的拓撲超導體研究。在本研究中，我們以自我助熔法成長FexBi2Te3 (x = 0.01、0.15)單晶樣品，並分別製作淬火及應變釋放(s-r)不同製程樣品，分別探討其電磁傳輸特性。我們在淬火樣品中發現c軸晶格常數的增加以及其電子作為主要載子的特性，此結果顯示鐵原子可能插層在碲化鉍的五層原子層(QL)間的凡得瓦層。在電性的量測中，我們發現在在溫度為5 K及磁場6T下，應變釋放Fe0.01Bi2Te3樣品具有巨大的磁阻(MR)約為760%，以及淬火Fe0.01Bi2Te3樣品，具有相當大的霍爾遷移率約為44000 cm2/Vs。最後我們試著分析淬火溫度為480 °C樣品的磁阻行為，發現在溫度T*約為100 K時，磁阻會由弱反局域效應(WAL)主導磁阻轉為線性及非飽和磁阻特性。我們發現在低溫下橫向磁導率(MC)能良好地以WAL關係式來描述，故載子傳輸可能仍為拓撲表面態保護下的散射機制；而在T>T*時高磁場下類線性磁阻行為，由於其磁界磁場B*符合量子極限體系，則可以由Abrikosov的狄拉克錐態的量子傳輸來解釋。

關鍵字

拓撲絕緣體 ； FexBi2Te3 ； 霍爾遷移率

並列摘要

Recently, topological materials have attracted interests. Topological insulator (TI) such as Bi2Se3 and Bi2Te3 with Dirac-cone suface states are used to study topological superconductors. In this work, we research electromagnetic transport properties of FexBi2Te3 (x=0.01, 0.15) single crystal sample prepared by self-flux method with quenching or strain-released(s-r) process. We find larger c-axis lattice constants and electron-dominant carriers in the quenched samples lead to imply that the Fe atoms are mostly located at the intercalated van der Waals gap between quintuple layers (QLs) of Bi2Te3. Large magnetoresistance (MR) of ∼760% was observed on a s-r Fe0.01Bi2Te3 sample and Hall mobility of ~44000 cm2/Vs on a quenched Fe0.01Bi2Te3 sample at 5 K under the magnetic field of 6 T.
Then we try to analyze MR behaviors in quenched Fe0.01Bi2Te3 sample with quenching temperature 480 °C, find a crossover from a weak antilocalization-dominant MR to a linear and non-saturating MR at temperatures of T*  100 K. At low temperatures, where the transverse magnetoconductivity(MC) can be well described by the WAL transport formula, so that topologically protected from backscattering is a possible mechanism. And it is found while the high-field linear-like MR at T > T* can be explained in terms of Abrikosov’s quantum transport of Dirac-cone states according to that critical field B*(T) could satisfy the regime of quantum limit.

並列關鍵字

topological insulator ； FexBi2Te3 ； Hall mobility

參考文獻

[1] X. L. Qi and S.C. Zhang, Rev. Mod. Phys. 83, 1057 (2011).

[2] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 146802 (2005).

[3] X. L. Qi,S. C. Zhang, Physics Today 63, 1, 33 (2010).

[4] C. Day, Physics Today, 61(1), 19 (2008).

[5] B. A. Bernevig and S. C. Zhang, Phys. Rev. Lett. 96, 106802 (2006).