论文标题
抗铁磁莫特绝缘子的量子自旋扭矩驱动的变异
Quantum spin torque driven transmutation of antiferromagnetic Mott insulator
论文作者
论文摘要
反铁磁性旋转型中的自旋转移扭矩（STT）的标准模型认为，流动电子的量子旋转与非旋转性局部旋转之间的角动量交换被视为经典载体。这些向量被认为可以实现均衡的néel订单，$ \ uparrow \ downrow \ ldots \ uparrow \ downarrow $，其STT驱动的动力学由Landau-Lifshitz-Gilbert（LLG）方程式描述。但是，许多实验使用的材料（例如原型NIO）是强烈的电子相关的抗铁磁莫特绝缘子（AFMI），其中局部旋转形成了与未接入的NéelNeelnate $ | \！\ \！\！ \ uparrow \ downarrow \ ldots \ uparrow \ downarrow \ rangle $。真实的基态被量子自旋波动纠缠在一起，从而导致所有局部旋转的期望值为零，因此甚至无法启动固定长度旋转的经典载体的LLG动力学。取而代之的是，对于捕获它们之间的旋转角动量的交换（表示为量子STT），需要对传导电子和局部自旋进行全量子处理。 We use a recently developed time-dependent density matrix renormalization group approach to quantum STT to predict how injection of a spin-polarized current pulse into a normal metal layer coupled to AFMI overlayer via exchange interaction and possibly small interlayer hopping -- which mimics, e.g., topological-insulator/NiO bilayer employed experimentally -- will induce nonzero expectation value of AFMI localized spins.这个新的非平衡阶段是一种在空间上不均匀的铁磁体，具有局部旋转的锯齿形曲线。 AFMI吸收的总自旋随着AFMI中的电子电子排斥而增加，以及两层不交换任何电荷时。
The standard model of spin-transfer torque (STT) in antiferromagnetic spintronics considers exchange of angular momentum between quantum spins of flowing electrons and noncollinear-to-them localized spins treated as classical vectors. These vectors are assumed to realize Néel order in equilibrium, $\uparrow \downarrow \ldots \uparrow \downarrow$, and their STT-driven dynamics is described by the Landau-Lifshitz-Gilbert (LLG) equation. However, many experimentally employed materials (such as archetypal NiO) are strongly electron-correlated antiferromagnetic Mott insulators (AFMI) where localized spins form a ground state quite different from the unentangled Néel state $|\!\! \uparrow \downarrow \ldots \uparrow \downarrow \rangle$. The true ground state is entangled by quantum spin fluctuations, leading to expectation value of all localized spins being zero, so that LLG dynamics of classical vectors of fixed length rotating due to STT cannot even be initiated. Instead, a fully quantum treatment of both conduction electrons and localized spins is necessary to capture exchange of spin angular momentum between them, denoted as quantum STT. We use a recently developed time-dependent density matrix renormalization group approach to quantum STT to predict how injection of a spin-polarized current pulse into a normal metal layer coupled to AFMI overlayer via exchange interaction and possibly small interlayer hopping -- which mimics, e.g., topological-insulator/NiO bilayer employed experimentally -- will induce nonzero expectation value of AFMI localized spins. This new nonequilibrium phase is a spatially inhomogeneous ferromagnet with zigzag profile of localized spins. The total spin absorbed by AFMI increases with electron-electron repulsion in AFMI, as well as when the two layers do not exchange any charge.
