Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands.
Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.
J Phys Condens Matter. 2022 Nov 25;35(3). doi: 10.1088/1361-648X/aca24e.
A 'toy model'-aimed at capturing the essential physics-is presented that jointly describes spin-polarized hot electron transport and spin pumping driven by local heating. These two processes both contribute to spin-current generation in laser-excited magnetic heterostructures. The model is used to compare the two contributions directly. The spin-polarized hot electron current is modeled as one generation of hot electrons with a spin-dependent excitation and relaxation scheme. Upon decay, the excess energy of the hot electrons is transferred to a thermalized electron bath. The elevated electron temperature leads to an increased rate of electron-magnon scattering processes and yields a local accumulation of spin. This process is dubbed as spin pumping by local heating. The built-up spin accumulation is effectively driven out of the ferromagnetic system by (interfacial) electron transport. Within our model, the injected spin current is dominated by the contribution resulting from spin pumping, while the hot electron spin current remains relatively small. We derive that this observation is related to the ratio between the Fermi temperature and Curie temperature, and we show what other fundamental parameters play a role.
我们提出了一个“玩具模型”，旨在捕捉基本物理，该模型共同描述了由局部加热驱动的自旋极化热电子输运和自旋泵浦。这两个过程都有助于激光激发磁性异质结构中的自旋电流产生。该模型用于直接比较这两个贡献。自旋极化热电子电流被建模为一代具有自旋相关激发和弛豫方案的热电子。在衰减过程中，热电子的多余能量被转移到热化的电子浴中。电子温度的升高导致电子-声子散射过程的速率增加，并导致自旋的局部积累。这个过程被称为局部加热的自旋泵浦。通过（界面）电子输运，建立的自旋积累有效地从铁磁系统中排出。在我们的模型中，注入的自旋电流主要由自旋泵浦产生的贡献主导，而热电子自旋电流仍然相对较小。我们得出的结论是，这种观察结果与费米温度和居里温度之间的比值有关，并且我们展示了其他基本参数的作用。
