Electrons in double-layer semiconductor heterostructures experience a special type of spin-orbit interaction which arises in each layer from the perpendicular component of the Coulomb electric field created by electron density fluctuations in the other layer. We show that this interaction, acting in combination with the usual spin-orbit interaction, can generate a spin current in one layer when a charge current is driven in the other. This effect is symmetry-wise distinct from the spin Hall drag. The spin current is not, in general, perpendicular to the drive current.
We analyze the experimentally obtained spin-current-related magnetoresistance in epitaxial Pt/Co bilayers by using a drift-diffusion model that incorporates both bulk spin Hall effect and interfacial Rashba-Edelstein effect (REE). The magnetoresistance analysis yields, for the Pt/Co interface, a temperature-independent Rashba parameter in the order of 1e-11 eV m that agrees with theoretical calculations, along with an effective interfacial REE thickness of several angstroms which is in overall consistency with our previous spin-orbit torque analysis. In particular, our results suggest that bot…
Inversion symmetry in bilayer graphene allows for layered opposite Rashba spin-orbit coupling (LO-RSOC) -- the situation when the RSOC has the same magnitude but the opposite sign in two coupled spatially separated layers. We show that the LO-RSOC results in the loss of spin chirality in the momentum space, in contrast to the common uniform RSOC. This chirality loss makes it difficult to experimentally establish whether the LO-RSOC (on the scale of 10 meV) exists, because the band structure is insensitive to it. To solve this problem, we propose to identify the LO-RSOC either by gating to brea…
We consider twisted bilayer and trilayer graphene in the presence of Rashba spin-orbit coupling and explore the physics of Moiré spintronics. The electronic charge density has a sharp step right at the magic angles $θ_m$. As a result, local spin observables (polarization and equilibrium spin currents) have sharp peaks (of width about a small fraction of 1$^\circ$) as a function of the twist angle $θ$, and abrupt sign reversals at $θ_m$. Thereby, the magic angle can be determined in an unprecedented accuracy. In the first chiral limit, the spin currents vanish, but the peculiar pattern of the p…
In this work, we have studied the spin-dependent ballistic transport and anomalous quantum tunnelling in Bilayer Graphene (BLG) hybrid connected to two Rashba-Zeeman (RZ) leads under an external electric biasing. We investigated the transmission and conductance for the proposed system using scattering matrix formalism and Landauer - Buttiker formula considering a double delta-like barrier under a set of experimentally viable parameters. We found that the transmission characteristics are notably different for up and down spin incoming electrons depending upon the strength of magnetization. More…
Topological insulators represent a new class of quantum phase defined by invariant symmetries and spin-orbit coupling that guarantees metallic Dirac excitations at its surface. The discoveries of these states have sparked the hope of realizing nontrivial excitations and novel effects such as a magnetoelectric effect and topological Majorana excitations. Here we develop a theoretical formalism to show that a three dimensional topological insulator can be designed artificially via stacking bilayers of two-dimensional Fermi gases with opposite Rashba-type spin-orbit coupling on adjacent layers, a…
Microscopic origin of Rashba coupling from first principles: Layer-resolved orbital asymmetry in transition metal dichalcogenides
University of Hamburg（汉堡大学）；Max Planck Institute for the Structure and Dynamics of Matter（马克斯·普朗克物质结构与动力学研究所）；The Hamburg Centre for Ultrafast Imaging（汉堡超快成像中心）
Van der Waals heterostructures formed by stacking different types of 2D materials are attracting increasing attention due to new emergent physical properties such as interlayer excitons. Recently synthesized atomically thin indium selenide (InSe) and antimony (Sb) individually exhibit interesting electronic properties such as high electron mobility in the former and high hole mobility in the latter. In this work, we present a first-principles investigation on the stability and electronic properties of ultrathin bilayer heterostructures composed of InSe and Sb single layers. The calculated elec…
Electrode-tunable nonlocal charge to spin conversion in WSe$_2$-intercalated bilayer graphene
Institute of Informatics, Slovak Academy of Sciences（斯洛伐克科学院信息学研究所）；Faculty of Physics, University of Belgrade（贝尔格莱德大学物理学院）；Institute of Physics, Pavol Jozef Šafárik University in Košice（科希策帕维尔·约瑟夫·沙法里克大学物理研究所）；Institute of Experimental Physics, Slovak Academy of Sciences（斯洛伐克科学院实验物理研究所）；New Technologies Research Centre, University of West Bohemia（西波希米亚大学新技术研究中心）
Coulomb drag experiments can give us information about the interaction state of double-layer systems. Here, we demonstrate anomalous Coulomb drag behaviours in a two-dimensional electron-electron bilayer system constructed by stacking atomically thin MoS2 on opposite sides of thin dielectric layers of boron nitride. In the low temperature regime, the measured drag resistance does not follow the behaviour predicted by the Coulomb drag models of exchanging momenta and energies with the particles in Fermi-liquid bilayer systems. Instead, it shows an upturn to higher and higher values. We investig…
The ability to control the strength of interaction is essential for studying quantum phenomena emerging from a system of correlated fermions. For example, the isotope effect illustrates the effect of electron-phonon coupling on superconductivity, providing an important experimental support for the BCS theory. In this work, we report a new device geometry where the magic-angle twisted bilayer graphene (tBLG) is placed in close proximity to a Bernal bilayer graphene (BLG) separated by a 3 nm thick barrier. Using charge screening from the Bernal bilayer, the strength of electron-electron Coulomb …
Wannier Function Approach to Realistic Coulomb Interactions in Layered Materials and Heterostructures
我们介绍了一种方法来获得现实的库仑相互作用项在独立的层状材料和垂直异质结构从从头计算模拟相应的散装材料。为此，我们建立了一个组合的计算框架内的约束随机相位近似，Wannier函数表示的库仑矩阵元素在一些低能量希尔伯特空间和连续介质静电，我们称之为Wannier函数连续静电（WFCE）。对于单层和双层石墨烯，我们再现完整的从头计算的库仑矩阵元素的精度为$0.2$ eV或更好。我们表明，在双层石墨烯中的现实库仑相互作用可以通过不同的电介质和金属环境在eV尺度上进行操纵。与[M. M. Scherer等人，Phys.Rev.B85，235408（2012）]提出双层石墨烯的电子基态是层状反铁磁体，并且令人惊讶地保持不受库仑相互作用中的这些强变化的影响。
Anomalous Coulomb Drag in Electron-Hole Bilayers due to the Formation of Excitons
最近的几个实验报道了电子空穴双层膜中库仑拖曳效应的反常温度依赖性。受这些令人困惑的数据的启发，我们从理论上研究了低密度电子空穴双层膜，其中电子和空穴通过形成激子分子来避免量子简并。我们描述了电子-空穴等离子体和激子气体之间的电离-复合交叉，并计算了层内电阻率和拖曳电阻率作为温度的函数。后者表现出一个最小值，然后在低温下急剧上升，与实验观察结果定性一致[见，例如，J. A. Wendons等人，物理修订版信函102，026804（2009）]。重要的是，拖曳电阻率在所提出的方案中被发现是相当不敏感的电子和空穴浓度的失配形成鲜明对比的情况下的电子-空穴库珀配对。
