Topological phase transition induced extreme magnetoresistance in TaSb$_{2}$
Topological phase transition induced extreme magnetoresistance in TaSb$_{2}$
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发表时间：
2016-03
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通讯作者：
Zheng Wang;Yupeng Li;Yunhao Lu;Zhixuan Shen;Feng Sheng;C. Feng;Yi Zheng;Zhu-An Xu
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作者：
Zheng Wang;Yupeng Li;Yunhao Lu;Zhixuan Shen;Feng Sheng;C. Feng;Yi Zheng;Zhu-An Xu
在1.5 K和15 T的温和条件下，我们报道了TaSb${2}$的1.72百万%的极大正磁电阻。二次增长的磁阻（MR $\propto\，B^{1.96}$）是不饱和高达15 T，一个几乎完美的补偿与电子和空穴之间的不匹配在这个半金属的表现。补偿机制被证实的温度依赖的MR，霍尔和热电系数的Nernst和Seebeck，揭示了两个明显的费米面重建过程没有自发对称性破缺，\textit{即}。Lifshitz转变，分别在20 K和60 K左右。利用磁阻和磁化率的量子振荡，并结合密度泛函理论计算，我们确定了TaSb${2}$的主空穴费米面沿$F-L$线形成了独特的沿着肩结构。该肩袋的平带顶部仅比费米能级高出几meV，导致在20 K时肩袋消失时观察到的拓扑相变。温度的进一步升高将费米能级推到主空穴袋的带顶，在60 K时，当空穴袋完全消失时，引起第二次Lifshitz跃迁。
We report extremely large positive magnetoresistance of 1.72 million percent in single crystal TaSb$_{2}$ at moderate conditions of 1.5 K and 15 T. The quadratic growth of magnetoresistance (MR $\propto\,B^{1.96}$) is not saturating up to 15 T, a manifestation of nearly perfect compensation with $<0.1\%$ mismatch between electron and hole pockets in this semimetal. The compensation mechanism is confirmed by temperature-dependent MR, Hall and thermoelectric coefficients of Nernst and Seebeck, revealing two pronounced Fermi surface reconstruction processes without spontaneous symmetry breaking, \textit{i.e.} Lifshitz transitions, at around 20 K and 60 K, respectively. Using quantum oscillations of magnetoresistance and magnetic susceptibility, supported by density-functional theory calculations, we determined that the main hole Fermi surface of TaSb$_{2}$ forms a unique shoulder structure along the $F-L$ line. The flat band top of this shoulder pocket is just a few meV above the Fermi level, leading to the observed topological phase transition at 20 K when the shoulder pocket disappears. Further increase in temperature pushes the Fermi level to the band top of the main hole pocket, induced the second Lifshitz transition at 60 K when hole pocket vanishes completely.