Hetényi Bence, Bosco Stefano, Loss Daniel
Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Phys Rev Lett. 2022 Sep 9;129(11):116805. doi: 10.1103/PhysRevLett.129.116805.
An anomalous energy splitting of spin triplet states at zero magnetic field has recently been measured in germanium quantum dots. This zero-field splitting could crucially alter the coupling between tunnel-coupled quantum dots, the basic building blocks of state-of-the-art spin-based quantum processors, with profound implications for semiconducting quantum computers. We develop an analytical model linking the zero-field splitting to the Rashba spin-orbit interaction that is cubic in momentum. Such interactions naturally emerge in hole nanostructures, where they can also be tuned by external electric fields, and we find them to be particularly large in silicon and germanium, resulting in a significant zero-field splitting in the μeV range. We confirm our analytical theory by numerical simulations of different quantum dots, also including other possible sources of zero-field splitting. Our findings are applicable to a broad range of current architectures encoding spin qubits and provide a deeper understanding of these materials, paving the way toward the next generation of semiconducting quantum processors.
最近在锗量子点中测量到了零磁场下自旋三重态的异常能量分裂。这种零场分裂可能会极大地改变隧道耦合量子点之间的耦合，而隧道耦合量子点是先进的基于自旋的量子处理器的基本组成部分，这对半导体量子计算机有着深远的影响。我们开发了一个分析模型，将零场分裂与动量立方的 Rashba 自旋轨道相互作用联系起来。这种相互作用在空穴纳米结构中自然出现，在那里它们也可以通过外部电场进行调节，并且我们发现它们在硅和锗中特别大，导致在 μeV 范围内有显著的零场分裂。我们通过对不同量子点的数值模拟证实了我们的分析理论，其中还包括零场分裂的其他可能来源。我们的发现适用于当前广泛的编码自旋量子比特的架构，并为深入理解这些材料提供了帮助，为下一代半导体量子处理器铺平了道路。
