Spin and charge currents through contacted quantum spin chains: A time-dependent density matrix renormalization group study

反铁磁金属和绝缘体是新型自旋电子器件中信息编码、传输和处理的理想材料，它们具有联合收割机的优良性能、高灵敏度、低能耗和易操作等优点。在这样的系统中，信号的传输是由代表自旋角动量流的自旋电流介导的，而不是由电荷电流介导的。为了使自旋电流进出有源反铁磁组件，可以在电写入、阅读和切换过程中利用（逆）自旋霍尔效应。在拟议的研究项目的范围内，我们通过在外部磁场中的（各向异性）量子自旋（1/2或1）链来模拟这样一个通用的自旋电子设置，夹在两个二维或三维引线（水库）之间，具有强大的Rashba或Dresselhaus型自旋轨道耦合，特别是计算通过设备的自旋和电荷电流。为此，我们结合联合收割机基本上无偏的数值技术，时间相关的密度矩阵重整化群方法（在矩阵产品状态为基础的制定）与块Lanczos递归或树张量网络计划。该算法将被并行化，并在大规模计算集群上实现。在我们的理论方法中，自旋链项有利于（更标准的）铁磁和反铁磁的情况下，预计将显示扩散和弹道输运行为，分别。此外，取决于自旋-自旋相互作用的各向异性，通过驱动自旋链实现无隙或有隙状态，具有显著不同的输运性质。在后一种情况下增加磁场强度，自旋激发间隙将减小并最终闭合，这提供了一种用于调谐/控制自旋电流的手段。在超越迄今为止现有的（而不是唯象的）自旋波电流的描述，我们在反铁磁系统的自旋电子学的位置来分析和量化的内在量子效应。我们还设想通过耦合到拓扑绝缘体的量子自旋链的自旋相关输运的调查。

Antiferromagnetic metals and insulators are promising candidates for encoding, transferring and processing information in novel spintronic devices, which combine excellent performance, high sensitivity, low energy consumption and easy handling. In such systems the transmission of signals is rather mediated by spin currents, representing a flow of spin angular momentum, than by charge currents. To get spin currents into and out of the active antiferromagnetic component, the (inverse) spin Hall effect can be exploited in the electrical writing, reading, and switching processes. Within the scope of the proposed research project, we model such a generic spintronic setup by an (anisotropic) quantum spin (1/2 or 1) chain in an external magnetic field, sandwiched between two two- or three-dimensional leads (reservoirs) with strong Rashba- or Dresselhaus-type spin-orbit coupling at play, and calculate, in particular, the spin and charge currents through the device. To this end, we combine basically unbiased numerical techniques, the time-dependent density-matrix renormalization group method (in a matrix-product-state based formulation) with the block Lanczos recursion or tree tensor network schemes. The algorithm will be parallelized and implemented on large-scale compute clusters. In our theoretical approach, the spin-chain term facilitates both (more standard) ferromagnetic and antiferromagnetic situations, expected to show diffusive and ballistic transport behavior, respectively. Furthermore, depending on the anisotropy of the spin-spin interaction, a gapless or gapful state is realized by the driven spin chain, with notably different transport properties. Increasing the magnetic field strength in the latter case, the spin excitation gap will be reduced and finally closed, which provides one mean for tuning/control the spin current. In going beyond the hitherto existing (rather phenomenological) descriptions of spin-wave currents we are in the position to analyze and quantify intrinsic quantum effects in the spintronics of antiferromagnetic systems. We also envisage the investigation of spin-dependent transport through quantum spin-chains coupled to topological insulators.