四錫化鉑、四錫化金和四鉛化鉑單晶之電磁傳輸特性的研究

Electromagnetic Transport Properties of PtSn4, AuSn4 and PtPb4 Single Crystals

沈棟(Dong Shen)

指導教授 ： 王立民

國立臺灣大學/理學院/物理學研究所/博士(2020年)

https://doi.org/10.6342/NTU202004148

摘要

最近幾年，拓撲絕緣體和拓撲超導體的研究引發了許多人的關注，比如具有狄拉克錐表面態的Bi2Te3和Cu0.3Bi2Se3。在本研究中，我們首先研究了拓撲材料PtSn4單晶的電磁傳輸特性。在溫度2.5 K及磁場6 T下觀察到約1860%的巨大磁阻，且磁阻行為可以用Abrikosov的量子傳輸理論來解釋。此外，PtSn4晶體表面可能還存在拓撲霍爾效應。
AuSn4和PtPb4都與拓撲PtSn4有相似的晶體結構。進一步，我們研究AuSn4和PtPb4的電磁傳輸特性。對於AuSn4單晶，我們通過BKT相變，玻色金屬相，二維磁通動力學驗證了其存在二維超導特性，Tc約為2.40 K。我們還發現低溫下的正常態電導可以用弱局域效應很好的描述，這種現象通常在拓撲材料中觀察到。這強烈的證明AuSn4正常態電磁傳輸特性是由拓撲狄拉克錐表面態電子所決定的。上述的所有結果最終綜合成為AuSn4晶體的相圖。對於於PtPb4單晶，我們同樣觀察到其存在二維超導特性，Tc約為2.80 K。此外，我們還在低溫正常態磁阻中發現其可能存在類似從AuSn4中觀察到的弱局域效應現象。通過本研究，結合二維超導和狄拉克錐表面態，AuSn4和PtPb4單晶中可能存在拓撲超導特性。

關鍵字

PtSn4 ； AuSn4 ； PtPb4 ； 拓撲材料 ； 二維超導

並列摘要

Recently, topological insulators and topological superconductors such as Bi2Te3 and Cu0.3Bi2Se3 with Dirac-cone suface state have attracted interests. In this work, we initially research the electromagnetic transport properties of topological material PtSn4 single crystals. Large magnetoresistance of ~1860% is observed at 2.5 K under a field of 6 T, and the magnetoresistance behaviors can be described by the Abrikosov’s quantum transport theory. Furthermore, a topological-Hall-effect-like phenomenon has been observed on the surface of PtSn4.
AuSn4 and PtPb4 are isostructural with the topological material PtSn4. Further, we study the transport properties of AuSn4 and PtPb4 single crystals. For AuSn4 single crystals, the superconductivity with a superconducting critical temperature Tc of ~2.40 K exhibits two-dimensional (2D) nature by showing evidence of a Berezinsky–Kosterlitz–Thouless (BKT) transition, Bose-metal phase, and the 2D flux vortex dynamics. It is found that the normal-state magnetoconductivity of AuSn4 at low temperatures can be well described by the weak-antilocalization (WAL) transport formula, which has been commonly observed on topological materials, strongly supporting the scenario that the normal-state magnetotransport in AuSn4 is dominated by the surface electrons in topological Dirac-cone states. The entire results can be summarized in a constructed phase diagram of AuSn4 crystals. For PtPb4 single crystals, the two-dimensional-like superconductivity with Tc of ~2.80 K can be observed. Moreover, a weak-antilocalization-like phenomenon has been observed in the low-temperature normal-state magnetoresistance like AuSn4. With the combination of 2D superconductivity and Dirac-cone surface states, this work reveals the drastic impact on the possible topological superconductivity in AuSn4 and PtPb4 single crystals.

並列關鍵字

PtSn4 ； AuSn4 ； PtPb4 ； topological material ； 2D superconductivity

參考文獻

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