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

通过接触量子自旋链的自旋和电荷电流：时间相关的密度矩阵重正化群研究

• 批准号: 344071920
• 负责人: Dr. Satoshi Ejima
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/344071920?language=en
• 关键词: Spin; charge; currents; through; contacted

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.

反铁磁性金属和绝缘体具有优异的性能、高灵敏度、低能耗和易操作等优点，在新型自旋电子器件的信息编码、传输和处理方面具有广阔的应用前景。在这样的系统中，信号的传输更多地由代表自旋角动量流的自旋电流来调节，而不是由电荷电流来调节。为了使自旋电流流入和流出有源反铁磁组件，可以在电写入、读取和开关过程中利用(逆)自旋霍尔效应。在拟议的研究项目范围内，我们模拟了这样一个一般的自旋电子装置，它是由一个(各向异性)量子自旋(1/2或1)链在外部磁场中夹在两个具有强烈Rashba或Dresselhaus类型的自旋-轨道耦合的二维或三维引线(库)之间建立的，并特别计算了通过该装置的自旋和电荷电流。为此，我们结合了基本无偏的数值技术，含时密度矩阵重整化群方法(基于矩阵乘积状态的形式)和块Lanczos递推或树形张量网络格式。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，自旋链项促进了(更标准的)铁磁和反铁磁两种情况，预计分别显示扩散和弹道输运行为。此外，根据自旋-自旋相互作用的各向异性，被驱动的自旋链实现了无间隙或有间隙状态，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，这为调谐/控制自旋电流提供了一种手段。超越了迄今存在的(相当唯象的)对自旋波电流的描述，我们能够分析和量化反铁磁系统自旋电子学中的本征量子效应。我们还设想了通过与拓扑绝缘体耦合的量子自旋链的自旋相关输运的研究。