Nonequilibrium quantum dynamics of current-driven magnetic skyrmions

磁性Skyrmions的拓扑保护使它们成为在技术赛道设备中可靠处理信息的有趣候选者。Skyrmion是一种具有非共线磁化的涡旋状自旋织构，可以在非中心对称的磁性化合物中形成。它们被视为相当稳定的准粒子，可以小到原子尺度，并且可以通过低密度的自旋极化电子流移动。它们的形成和控制是非平凡的动力学过程（由于拓扑保护），需要涉及耗散的非平衡过程，正如我们在上一个资助期所述。此外，它们在杂质团簇存在下的动力学显示了报告中描述的各种现象。虽然在过去已经进行了先进的动力学模拟，我们打算在未来的资助期间，以解决的Skyrmions和Antiskyrmions的动力学稳定性的问题，在一个潜在的能源景观在存在的外部电流作为适当的变形参数的函数。我们的目标是获得一个Kramers率理论的Skyrmions的稳定性。此外，我们将把我们的重点放在反铁磁Skyrmions，这是有趣的，因为除了提到的Skyrmions的功能，一个反铁磁主机与零总磁化是磁性相当惰性，但在成本上，外部操纵电流是不平凡的。特别是电流的存在，驱动系统远离其基态激发了反铁磁体的理论描述超出平均场理论的两个耦合铁磁子晶格。我们计划发展这样一个理论的电流驱动的反铁磁Skyrmions超越平均场理论，通过扩展后者的自旋波波动。我们预见新的贡献的自旋转移力矩。此外，我们还将研究驻留在晶格位置的量子自旋所形成的真实的量子Skyrmions。我们打算扩展我们的初步量子模拟，解决稳定性和量子力学与经典拓扑概念的相互作用的问题。最后，我们计划研究由点状发射体的圆形自旋波驱动的磁性Skyrmions的动力学。这一概念在技术上与潜在的设备相关，并且在Stefan Krause博士（汉堡大学）的项目中也进行了实验研究，我们计划与他合作开展本优先计划。

The topological protection of magnetic Skyrmions renders them interesting candidates for the reliable processing of information in technological racetrack devices. Skyrmions are vortex-like spin textures with non-collinear magnetization that can be formed in non-centrosymmetric magnetic compounds. They are viewed as quasiparticles that are rather stable, can be small in size down to the atomic scale and can be moved by low densities of spin-polarized electronic currents. Their formation and their control are nontrivial dynamical processes (due to topological protection) and require nonequilibrium processes involving dissipation, as we have described in the previous funding period. Moreover, their dynamics in the presence of impurity clusters shows a variety of phenomena described in the report. While well advanced dynamical simulations have been carried out in the past, we intend in the coming funding period to address the question of the dynamical stability of Skyrmions and Antiskyrmions in terms of a potential energy landscape in the presence of an external current as a function of suitable deformation parameters. We aim to obtain a Kramers rate theory for the stability of the Skyrmions. Furthermore, we will turn our focus to antiferromagnetic Skyrmions which are interesting because in addition to the mentioned features of Skyrmions, an antiferromagnetic host with zero total magnetization is magnetically rather inert, yet on the cost that an external manipulation by a current is non-trivial. Especially the presence of a current which drives the system away from its groundstate motivates a theoretical description of the antiferromagnet beyond mean-field theory for two coupled ferromagnetic sublattices. We plan to develop such a theory of current-driven antiferromagnetic Skyrmions beyond mean-field theory by extending the latter by spin-wave fluctuations. We foresee novel contributions to the spin transfer torque. Moreover, we shall study real quantum Skyrmions formed by quantum spins residing at the lattice sites. We intend to extend our preliminary quantum simulations, addressing the questions of stability and the interplay of quantum mechanics with the classical concept of topology. Finally, we plan to investigate the dynamics of magnetic Skyrmions driven by circular spin waves from point-like emitters. This concept is technologically relevant for potential devices and is also studied experimentally in the project of Dr. Stefan Krause (Universität Hamburg) with whom we plan to collaborate in the present Priority Programme.