Evidence for massive bulk Dirac fermions in Pb1-xSnxSe from Nernst and thermopower experiments
Evidence for massive bulk Dirac fermions in Pb1-xSnxSe from Nernst and thermopower experiments
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DOI：
10.1038/ncomms3696
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发表时间：
2013-11-01
影响因子：
16.6
通讯作者：
Ong, N. P.
中科院分区：
文献类型：
--
作者：
Liang, Tian;Gibson, Quinn;Ong, N. P.
受镜像对称保护的拓扑表面态在自旋电子应用中具有重要意义。这些状态被预测存在于岩盐IV-VI半导体中，并且有几个小组利用光电发射观察到（Pb,Sn）Te, (Pb,Sn)Se和SnTe的表面状态。该理论的一个基本假设是，表面状态是由可描述为大质量狄拉克状态的体态产生的，但这个假设未经检验。在这里，我们证明了体态的热电响应显示了狄拉克谱特有的特征。通过将载流子密度与量子振荡中的峰值联系起来，我们证明了第一（N = 0）朗道能级是非简并的。这一发现提供了有力的证据，证明体态确实是大质量狄拉克态。在最低朗道能级，S-xx随狄拉克费米子的磁场特征呈显著的线性增长。此外，在低温下，能斯特信号在间隙反转相位中表现出符号异常。
Topological surface states protected by mirror symmetry are of interest for spintronic applications. Such states were predicted to exist in the rocksalt IV-VI semiconductors, and several groups have observed the surface states in (Pb,Sn)Te, (Pb,Sn)Se and SnTe using photoemission. An underlying assumption in the theory is that the surface states arise from bulk states describable as massive Dirac states, but this assumption is untested. Here we show that the thermoelectric response of the bulk states displays features specific to the Dirac spectrum. By relating the carrier density to the peaks in the quantum oscillations, we show that the first (N = 0) Landau level is non-degenerate. This finding provides robust evidence that the bulk states are indeed massive Dirac states. In the lowest Landau level, S-xx displays a striking linear increase versus magnetic field characteristic of massive Dirac fermions. In addition, the Nernst signal displays a sign anomaly in the gap-inverted phase at low temperatures.