單晶四碲化三鉑低溫電磁傳輸特性之研究

本研究藉由量測分析Pt3Te4之電磁傳輸來確認Pt3Te4是否如先前理論計算結果為拓撲半金屬，Pt3Te4單晶由自我助熔法合成，並經過X光繞射分析後確認為c軸朝上之單晶，從電性分析上本研究取兩個樣品各別做分析比較，發現雖然取樣上尺寸些許不同但在低溫下電性並沒有太大的區別大約在~0.5 µΩcm，傳輸載子為p-type濃度約1021~1022 cm-3，再零磁低溫下Pt3Te4具有費米液體的特徵，比熱分析上Pt3Te4之Kadowaki-Woods係數RKW~10-6 µΩ cm/(mole K /mJ)^2，在低溫2.5K有觀察到~90%磁阻，本實驗透過施加不同方向的磁場做磁阻分析，磁場垂直電流方向之線性不飽和磁阻可以用PL-model做解釋，而磁場平行電流時在低溫下量測出拓撲半金屬才有的負磁阻，此外在2.5 K之負磁阻可以用Adler-Bell-Jackiw Anomaly之模型做良好的擬合，磁性分析上Pt3Te4之大塊單晶在10 K以下小於臨界磁場0.2 T的範圍中有順磁性的趨勢，評估為拓撲絕緣體中狄拉克錐表面態的狄拉克費米子的磁反應所造成的現象。

關鍵字

拓撲半金屬；自我助溶法；狄拉克費米子； Pt3Te4

並列摘要

Pt3Te4 was considered a topological semimetal candidate by previously theoretical study. Therefore, in the research we tried to identify Pt3Te4 single crystals by studying low-temperature electro-transport. The Pt3Te4 single crystal were prepared by the self-flux method. In this work, we prepared two Pt3Te4 single crystals with difference sizes as probed samples. The results of electrical measurements indicate that Pt3Te4 performs metal-like transport properties such as high electrical conductance and fermi liquid behavior at low temperature(T<50 K). Similarly, The metal-like behavior was clarified by Kadowaki-Woods value of ~10-6 µΩ cm/(mole K /mJ)^2 calculated from resistivity and specific heat measurements. We observed high transverse magnetoresistance (TMR)~90% at 2.5 K under 6 T magnetic field. Furthermore, we founded that the negative longitude magnetoresistance (NLMR) phenomenon at low temperature region (T=2.5 K), which is considered as the fingerprint of topological semimetal, strongly supporting the scenario that chirality anomaly magnetic transport in Pt3Te4. Interestingly, in the dc magnetic measurement of single crystal of Pt3Te4, we observed cusp-like low-field paramagnetic response (H<0.2T) at low temperatures(T<10K). The low field paramagnetic response can be described by the Dirac fermion spin response of magnetic field in the Dirac cone surface state.