The spin of the electron is nowadays replacing the charge as basic carrier of information not only in spintronics applications, but also in the emerging field of quantum information. Topological quantum materials, where spin-momentum locking is believed to lead to particularly long spin lifetimes, are regarded as a promising platform for such applications. However, spin-orbit coupling, that is essential to all topological matter, at the same time gives rise to spin mixing and decoherence as a major obstacle for quantum computing. Here, we give experimental evidence that hot-spots of spin-mixing and spin-conserving contributions of the spin-orbit operator coexist in an archetypal topological Dirac metal, and that these hot spots can have a strongly anisotropic distribution of their respective wave vectors with respect to the spin quantization direction. Our results can be understood within a theory that takes into account the decomposition of the spin-orbit Hamiltonian into spin-conserving and spin-flip terms, contributing to a better understanding of quantum decoherence in topological materials, in general.

如今，电子的自旋不仅在自旋电子学应用中，而且在新兴的量子信息领域中都取代了电荷成为信息的基本载体。自旋动量锁定被认为导致特别长的自旋寿命的拓扑量子材料被认为是此类应用的有前途的平台。然而，自旋轨道耦合对所有拓扑物质都是必不可少的，同时也会引起自旋混合和退相干，这是量子计算的主要障碍。在这里，我们给出了实验证据，表明自旋轨道算子的自旋混合和自旋守恒贡献的热点共存于原型拓扑狄拉克金属中，并且这些热点可以具有它们各自的波向量相对于自旋量化方向的强烈各向异性分布。我们的结果可以在一个理论中理解，该理论将自旋轨道哈密顿量分解为自旋守恒和自旋翻转项，有助于更好地理解拓扑材料中的量子退相干，一般来说。