Guo Binghao, Miao Wangqian, Huang Victor, Lygo Alexander C, Dai Xi, Stemmer Susanne
Materials Department, University of California, Santa Barbara, California 93106-5050, USA.
Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China.
Phys Rev Lett. 2023 Jul 28;131(4):046601. doi: 10.1103/PhysRevLett.131.046601.
We report a topological phase transition in quantum-confined cadmium arsenide (Cd_{3}As_{2}) thin films under an in-plane Zeeman field when the Fermi level is tuned into the topological gap via an electric field. Symmetry considerations in this case predict the appearance of a two-dimensional Weyl semimetal (2D WSM), with a pair of Weyl nodes of opposite chirality at charge neutrality that are protected by space-time inversion (C_{2}T) symmetry. We show that the 2D WSM phase displays unique transport signatures, including saturated resistivities on the order of h/e^{2} that persist over a range of in-plane magnetic fields. Moreover, applying a small out-of-plane magnetic field, while keeping the in-plane field within the stability range of the 2D WSM phase, gives rise to a well-developed odd integer quantum Hall effect, characteristic of degenerate, massive Weyl fermions. A minimal four-band k·p model of Cd_{3}As_{2}, which incorporates first-principles effective g factors, qualitatively explains our findings.
我们报道了在面内塞曼场作用下，量子限制砷化镉（Cd₃As₂）薄膜中的一种拓扑相变，此时费米能级通过电场被调节到拓扑能隙中。在这种情况下，对称性考虑预测会出现二维外尔半金属（2D WSM），在电荷中性时具有一对相反手性的外尔节点，它们受时空反演（C₂T）对称性保护。我们表明，2D WSM相表现出独特的输运特征，包括在一系列面内磁场中持续存在的约为h/e²量级的饱和电阻率。此外，在保持面内磁场处于2D WSM相的稳定范围内时，施加一个小的面外磁场会产生一个发育良好的奇整数量子霍尔效应，这是简并、有质量的外尔费米子的特征。包含第一性原理有效g因子的Cd₃As₂的最小四能带k·p模型定性地解释了我们的发现。
