Weyl半金属Pb$_{1-x}$Sn$_x$Te:Cr合金中电子磁输运的可调手性异常
Tunable chiral anomaly in electron magnetotransport in the Weyl semimetallic Pb$_{1-x}$Sn$_x$Te:Cr alloy
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中文总结 AI 辅助
本研究制备重掺Cr的Pb$_{1-x}$Sn$_x$Te晶体，在0.25<x<0.45时观测到三维Weyl半金属相，验证了化学无序与Cr掺杂对费米能级的调控作用及Berry曲率与电学性质的关联。
中文摘要 AI 辅助
我们研究半导体置换合金Pb$_{1-x}$Sn$_x$Te的磁输运性质，该合金具有依赖Sn含量的拓扑晶体绝缘体性质，在特定带反转点处呈现半金属零能隙态。我们实验验证了该多谷电子系统中化学无序的理论预测作用，化学无序导致不同谷中发生连续带反转，并使费米能级靠近Weyl节点对，这一结果在密度泛函理论计算中得到证实。混合价Cr共振杂质的掺杂可利用掺杂共振态的独特性质，为调控载流子浓度提供有效手段。上述两种效应的结合使费米能级在宽成分范围内被钉扎在节点接触点附近。为解决上述问题，我们制备了重掺Cr且覆盖全Sn含量范围（0 ≤ x ≤ 1）的Pb$_{1-x}$Sn$_x$Te Bridgman块状晶体，涵盖拓扑晶体绝缘体和普通电子态两种区域。我们在一定Sn含量范围内观察到三维（3D）Weyl半金属相的出现，即0.25 < x < 0.45，我们为此提供了磁输运证据，并验证了实验确定的Berry曲率大小与这些材料电学性质之间的关系。磁电阻中观测到的量子输运机制也通过热导率测量得到独立证实。
英文摘要
We study magnetotransport properties of semiconductor substitutional alloy Pb$_{1-x}$Sn$_x$Te, known to exhibit Sn-content dependent properties of topological crystalline insulators with a semimetallic zero-gap state at a specific band inversion point. We experimentally verify the theoretically predicted role of chemical disorder in this multivalley electron system, which leads to sequential band inversions in various valleys and places the Fermi level close to the pairs of Weyl nodes, as identified in the density functional theory calculations. Doping with mixed-valence Cr resonant impurities enables exploitation of the unique properties of dopant resonant states, which provide an effective means of tuning carrier concentration. The combination of these two effects results in the pinning of the Fermi level in the vicinity of the nodal touching points across a wide range of composition. To address the above issues, we grow Bridgman bulk crystals of Pb$_{1-x}$Sn$_x$Te heavily doped with chromium and covering the full range of tin (0 $\leq x \leq$ 1), i.e. spanning both the topological crystalline insulator and trivial electronic regimes. We observe the emergence of the three dimensional (3D) Weyl semimetal phase over a range of Sn compositions, namely for $0.25 < x < 0.45$. We provide magnetotransport evidence for this and verify the relationship between the magnitude of the experimentally determined Berry curvature and the electrical properties of these materials. Quantum transport regime observed in magnetoresistance is also independently confirmed by thermal conductivity measurements.
