【作者】 张勇；

【导师】 宋凤麒； 王伯根；

【作者基本信息】 南京大学 ， 凝聚态物理， 2020， 硕士

【摘要】 拓扑物态近年来日益成为凝聚态物理中热门研究领域。从Kosterlitz-Thouless相变到TKNN不变量,从量子Hall效应到量子自旋Hall效应,人们对凝聚态物理中拓扑的概念理解更加深刻。以HgTe/CdTe量子阱为起点,至今已发展出多种拓扑材料,比如拓扑绝缘体和拓扑半金属等等。这些拓扑材料中出现了许多新奇的物性,也为未来电子工业发展提供了材料备选。非饱和的大磁阻是固体材料中一种有趣的输运现象。我们通过高达38 T的强磁场测量,在拓扑绝缘体候选材料TaSe3中观测到了 103%量级的大磁阻现象。同时,Shubnikov-de Hass量子振荡表明Fermi面附近有两个振荡频率。通过和第一性原理计算对比,说明这两个振荡频率来源于一个空穴口袋和两个相同的电子口袋。进一步通过细致的Hall输运测量,我们的两带模型拟合发现在稳定低于20 K时,载流子浓度比nh/ne大约为0.9,表明TaSe3中的大磁阻现象来源于载流子补偿机制。超导现象是凝聚态物理中常见的输运现象。我们通过系统地研究Mol-xTaxTe2的输运性质,发现随着Ta掺杂量的增加,MO1-xTaxTe2出现了同机械压力下相似的1T’到Td的结构相变和超导相变,且其c轴层间距也出现了减小的趋势。通过计算,我们发现结构相变同计算结果吻合。更多还原

【Abstract】 Topological phases have attracted research attention in the area of condensed matter physics recently.From Kosterlitz-Thouless transition to TKNN topological invariant,and quantum Hall effect to quantum spin Hall effect,the concept of topology in condensed matter physics has been understood much deeper.Starting with HgTe/CdTe quantum well,various topological materials have been exploited,such as topological insulators and topological semimetals,etc.The emergence of such topological materials brings many exotic phenomena,and these materials could be an option for the material basis of the future electronic industry.Large unsaturated magnetoresistance(XMR)is an interest of transport phenomenon in solids.Such magnetoresistance with magnitude～103%is observed in topological insulator candidate TaSe3 from our high field(up to 38 T)measurements.Two oscillation modes,associated with one hole pocket and two identical electron pockets in the bulk,respectively,are detected from our Shubnikov-de Hass measurements,consistent with our first-principles calculations.With the detailed Hall measurements performed,our two-band model analysis exhibits an imperfect density ratio nh/ne≈0.9 at T<20 K,which suggests that the carrier compensations account for the XMR in TaSe3Superconductivity is a regular in the transports of condensed matter physics.We systematically studied the transports of Mo1-xTaxTe2,and observe that Mo1-xTaxTe2 exhibits the 1T’-Td structural phase transition,metal-superconductor transition and the decreasing distance between layers along c-axis,with Ta substitution increasing,similar to the case of MoTe2 under applied pressure.With the calculations carried out,we found that the calculated results match the experimental data.更多还原