论文标题
从约束的紧密结合电子结构理论中获得绝热旋转动力学和有效的交换相互作用:超越海森堡政权
Adiabatic spin dynamics and effective exchange interactions from constrained tight-binding electronic structure theory: Beyond the Heisenberg regime
论文作者
论文摘要
我们考虑在电子结构的紧密结合描述中实现绝热旋转动力学方法。自由度自由度的绝热近似假定,更快的电子自由度始终处于准平衡状态,这与完整的电子动力学相比大大降低了数值复杂性。非结合磁性构型通过约束场稳定,这允许直接从约束场的阴性获得有效磁场。尽管显示动力学可以节省能量,但我们证明,当允许磁矩的长度变化时,绝热旋转动力学并不能保留总自旋角动量,这通过数值模拟证实。此外,我们开发了一种从非共线态的能量曲率张量提取有效的两旋交换相互作用的方法,我们在数值模拟的每个时间步骤中计算出来。我们证明了非共线性对这种有效交换的影响以及由于强烈的非共线配置中的多型旋转相互作用而引起的局限性,超出了海森伯格模型有效的制度。讨论了遵循磁性超快速动力学的实验泵探针实验,讨论了结果的相关性。
We consider an implementation of the adiabatic spin dynamics approach in a tight-binding description of the electronic structure. The adiabatic approximation for spin-degrees of freedom assumes that the faster electronic degrees of freedom are always in a quasi-equilibrium state, which significantly reduces the numerical complexity in comparison to the full electron dynamics. Non-collinear magnetic configurations are stabilized by a constraining field, which allows to directly obtain the effective magnetic field from the negative of the constraining field. While the dynamics are shown to conserve energy, we demonstrate that adiabatic spin dynamics does not conserve the total spin angular momentum when the lengths of the magnetic moments are allowed to change, which is confirmed by numerical simulations. Furthermore, we develop a method to extract an effective two-spin exchange interaction from the energy curvature tensor of non-collinear states, which we calculate at each time step of the numerical simulations. We demonstrate the effect of non-collinearity on this effective exchange and limitations due to multi-spin interactions in strongly non-collinear configurations beyond the regime where the Heisenberg model is valid. The relevance of the results are discussed with respect to experimental pump-probe experiments that follow the ultra-fast dynamics of magnetism.