半金属PtBi2和MoTe2的输运性质研究

  作为一类新型拓扑物质，对拓扑半金属的研究一直处于凝聚态物理的前沿。由于其独特的能带结构，拓扑半金属成为了相对论费米子的绝佳观测平台，其所具有的极大的磁阻、手性反常和本征反常霍尔效应等奇特的输运性质引起了诸多研究人员的关注。本论文旨在对两种拓扑半金属候选材料黄铁矿型PtBi₂和1T'相MoTe₂进行输运性质研究，以探测它们的基本电学和电子态拓扑属性，出于研究需要还发展了一些二维薄膜的器件制备方法。

  本论文主体分为四部分。（1）研究背景和意义。（2）实验设备和测量手段。（3）黄铁矿型PtBi₂的费米面结构研究。本文分别通过测量黄铁矿型PtBi₂的热电效应Shubnikov-de Hass（SdH）和 de Hass-van Alphen（dHvA）量子振荡，探测到PtBi₂的四个不同的量子振荡基频频率，明确了PtBi₂至少具有四个费米口袋。此外，根据立体空间转角的量子振荡频率的变化、有效回旋质量等多个特征参数，进一步确立各个电子费米口袋的空间分布及其电子拓扑结构属性。（4）二维薄膜的器件制备方法及1T'相MoTe₂的输运性质研究。本文研究了1T'相MoTe₂少层薄膜器件的制备方法以及输运性质。由于MoTe₂的层间作用力较大并且表面对水氧非常敏感，这给MoTe₂少层薄膜的研究带来了很大困难。针对这些困难，本文发展了新的薄膜制备和器件封装方法。最终实现了对少层1T'相MoTe₂本征材料器件的电学输运性质表征，并观测到它的伊辛超导特性。此外，本文还在微纳器件制备过程中意外发现了一个有趣的现象：铟电极与1T'相MoTe₂接触后会沿着MoTe₂薄膜和金膜表面扩散。这些结果为进一步开展同类型材料及其器件制备的研究奠定了良好的基础。

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