Topological nature of higher-order hinge states revealed by spin transport

自旋输运揭示高阶棱态的拓扑性质

One-dimensional(1D)gapless hinge states are predicated in the three-dimensional(3D)higher-order topological insulators and topological semimetals,because of the higher-order bulk-boundary correspondence.Nevertheless,the topologically protected property of the hinge states is still not demonstrated so far,because it is not accessible by conventional methods,such as spectroscopy experiments and quantum oscillations.Here,we reveal the topological nature of hinge states in the higher-order topological semimetal Cd;As;nanoplate through spin potentiometric measurements.The results of current induced spin polarization indicate that the spin-momentum locking of the higher-order hinge state is similar to that of the quantum spin Hall state,showing the helical characteristics.The spin-polarized hinge states are robust up to room temperature and can nonlocally diffuse a long distance larger than 5μm,further indicating their immunity protected by topology.Our work deepens the understanding of transport properties of the higher-order topological materials and should be valuable for future electronic and spintronic applications.

根据高阶拓扑相理论,在三维高阶拓扑材料中,除了常见的三维体态和二维表面态,还存在一维无能隙的拓扑棱态.由于很难通过传统的实验手段(如光谱和量子振荡测量)对一维电子态进行探测,到目前为止,人们对于棱态的拓扑性质仍然知之甚少.本文通过自旋电位测量的手段,揭示了高阶拓扑半金属Cd;As;纳米片中棱态的拓扑特性.实验发现,高阶棱态具有和量子自旋霍尔态类似的电子螺旋性特征,即棱态电子的自旋和动量是相互锁定的.棱态自旋极化信号能稳定维持到室温条件,且可以实现长距离的非局域传输,传输距离超过5μm.棱态自旋信号的温度鲁棒性和长程非局域传输特性,表明棱态由于受拓扑保护具备较强的抗环境干扰能力.该工作不但深化了人们对于高阶拓扑材料输运性质的理解,而且也为实现低功耗自旋电子学器件提供了重要的材料平台.