FOR 912: Coherence and Relaxation Properties of Electron Spins

自旋是电子的额外自由度，它可以导致当前基于电荷的信息处理范式的变化。在新兴的自旋电子学领域中，提出的新信息单元方案包括自旋阀、自旋晶体管和自旋量子位。所有这些概念都需要较低的自旋弛豫率和量子比特自旋态的相干性。在这方面，到目前为止，二元半导体已经得到了深入的研究，但很明显，替代材料在自旋弛豫和相干性方面可能更有利。特别是，碳基材料，如碳纳米管或石墨烯，最终可以提供更低的自旋弛豫和退相干，因为它们受自旋轨道和超精细耦合的影响较小。其他，甚至不太传统的材料，如一维量子磁体，可能通过提供纯自旋激发而更有前景，从而在特定系统中产生本质上无耗散的自旋输运。重要的是，对于c基材料和迫切需要探索性研究的量子磁体来说，自旋退相干和弛豫的限制通道都是未知的。在这个研究单元中，我们将处理自旋弛豫和相干的基本原理。一方面，我们将研究iii - v型半导体，作为参考和模型系统，介绍关于自旋相干性和操纵的新颖前沿方法。另一方面，我们将通过确定其动态自旋特性和引入设想的自旋功能的新概念来解决新材料。在所有三种材料类别中，自旋动力学的复杂性质需要强大的理论支持，包括新颖的数值方法，以便广泛应用于不同的材料类别。这些方法将基于当前的前沿方法，如DFT、QMC或TD-DMRG。

The spin is the additional degree of freedom of an electron, which can lead to a change in paradigm of present-day charge-based information processing. Within the emerging field of spintronics, proposed schemes for novel information units include, e.g., spin valves, spin transistors and spin qubits. All these concepts require a low spin relaxation rate and for qubits the coherence of spin states. In this respect, binary semiconductors have been intensively studied so far, but it is apparent that alternative materials are potentially more advantageous with respect to spin relaxation and coherence. In particular, carbon based materials such as carbon nanotubes or graphene could ultimately provide a reduced spin relaxation and decoherence, since they are less affected by spin-orbit and hyperfine coupling. Other, even less conventional materials such as one-dimensional quantum magnets might be even more prospective by providing pure spin excitations, resulting in an intrinsically dissipationless spin transport for particular systems. Importantly, the limiting channels for spin decoherence and relaxation are neither known for the C-based materials nor for the quantum magnets strongly requiring exploratory research. Within this Research Unit, we will tackle the fundamentals of spin relaxation and coherence. On the one hand, we will investigate the III-V-semiconductors, which serve as a reference and as model systems to introduce novel cutting-edge methodology with respect to spin coherence and manipulation. On the other hand, we will tackle the novel materials by determining their dynamic spin properties and introducing novel concepts for an envisioned spin functionality. In all three material classes, the intricate nature of spin dynamics requires a strong theoretical backing including novel numerical methods for a versatile application to the different material classes. These approaches will be developed based on the current forefront approaches in, e.g., DFT, QMC or TD-DMRG.