拓扑边缘态的曲率调控、隧穿时间、等离激元

The helical edge states in two-dimensional topological insulators have attracted extensive attention in condensed matter physics and material science. However, for the transport properties of edge-state devices, studies on curvature control and tunneling time are scarce. A recent work revealed the special spin orientation of helical edge states in bent ribbons, which offers the possibility to utilize the boundary degree of freedom (two opposite edges) of edge states as "like-spin" for information carriers. In recent years, the explorations on topological edge states have spread to some Bosonic systems. The studies on topological edge modes in two-dimensional plasmons are unfolding. This project is devoted to investigating several transport properties of topological edge states and their manipulations via external fields. By means of theoretical analysis and numerical simulation, we will reveal the features and related physical mechanism from the energy spectrum and lateral decay length of edge states, tunneling time, quantum interference, spin transport，and control of boundary position. The results are expected to provide theoretical basis and physical models for the development of electronic and optical devices at nanoscale and spintronic devices based on topological edges. The research subjects include: (1) transport properties in bent ribbons related to helical edge states; (2) tunneling time in helical-edge-state electron devices and its manipulation; (3) edge plasmons with tunable boundary position and edge modes under the effect of quantum pressure.

二维拓扑绝缘体中的螺旋边缘态在凝聚态物理及材料科学等领域得到广泛关注，但对边缘态器件输运性质的曲率调控、隧穿时间等方面的研究并不多见。最近的研究表明弯曲条带中的螺旋边缘态具有独特的自旋取向。这为利用边缘态的边界自由度(两个相对的边界)作为载荷信息的“类自旋”提供了可能性。近几年来，拓扑边缘态的探索扩展到一些玻色子体系，对二维等离激元拓扑边缘模式的研究则方兴未艾。本项目致力于研究拓扑边缘态的若干输运特性及外场调控。通过理论分析结合数值模拟，我们将从边缘态的能谱及横向衰减长度、隧穿时间、量子干涉、自旋输运、边界位置调控等方面揭示其中的规律和物理机制，为研制基于拓扑边缘态的纳米光电器件和自旋电子器件提供理论依据和物理模型。研究内容包括：(1) 弯曲条带中螺旋边缘态相关的输运性质；(2) 螺旋边缘态电子器件的隧穿时间及调控；(3) 边界位置可调的边缘等离激元及考虑量子压强效应时的边缘模式。

具有奇异能谱的低维材料在电场、磁场、光场、应变等调制下的输运性质是凝聚态物理的前沿主题之一。本项目开展的研究内容包括：(1) 无能隙拓扑态的磁输运；(2) 低维体系的非线性输运；(3) 石墨烯边缘等离激元的调控；(4) 粘滞电子流体的磁电阻调控。取得的重要研究结果如下。.(1) 针对具有倾斜狄拉克锥、半狄拉克点、各向异性表面态等无能隙拓扑态的材料，展示了广义克莱因隧穿导致的谷极化、能隙依赖的各项异性磁阻、源于侧面朗道能级的束缚态等效应，为在这些材料中实现谷电子学和新的磁输运现象提供参考。.(2) 从非线性响应的角度，研究了基于磷烯纳米条带的三端弹道结、应变磷烯的光致电流、超强激光脉冲下碳纳米管的电子发射、神经网络预测无序体系输运的可靠性。展示了强烈的传输各项异性在纳米电子学应用方面的独特优势以及光电流的力学调控，给出了与实验测量定性相符的电子发射谱，揭示了普适电导涨落对神经网络预测输运性质的性能限制。.(3) 针对石墨烯的边缘等离激元，研究了应变、THz多重谐频脉冲、Berry磁通等对其谷极化、色散、手征性、横向受限长度等的影响。通过自洽求解具有非线性项的二流体模型，展示了边缘等离激元谷极化的静态调控和动态调控。揭示了石墨烯边缘等离激元性质对边界条件的依赖，与实验结果定性相符。.(4) 研究了平面内的磁场梯度如何影响具有高g因子的二维粘滞电子系统的直流和交流磁电阻。展示了弱磁场下的负磁阻、长波等离激元的抑制、磁声共振峰的增强等效应，为粘滞电子流体磁声共振的实验测量、光电阻及光伏效应的调控提供新方案。