Quantum spin Hall insulators are two-dimensional materials that host conducting helical electron states strictly confined to the one-dimensional boundaries. These edge channels are protected by time-reversal symmetry against single-particle backscattering, opening new avenues for spin-based electronics and computation. However, the effect of the interelectronic Coulomb repulsion also has to be taken into account, as two-particle scattering is not impeded by topological protection and may strongly affect the edge state conductance. Here, we explore the impact of electronic correlations on highly localized edge states of the unique quantum spin Hall material bismuthene on SiC(0001) (ref. ¹). Exploiting the advantage of having an accessible monolayer substrate system, we use STM/STS to visualize the close-to-perfect one-dimensional confinement of the edge channels and scrutinize their suppressed density of states at the Fermi level. On the basis of the observed spectral behaviour and its universal scaling with energy and temperature, we demonstrate the correspondence with a (helical) Tomonaga–Luttinger liquid. In particular, the extracted interaction parameter K is directly relevant to the fundamental question of the temperatures at which the quantized conductance (a hallmark of quantum spin Hall materials) will become obscured by correlations².

量子自旋霍尔绝缘体是二维材料，具有严格限制在一维边界内的传导螺旋电子态。这些边缘通道受到时间反转对称性的保护，以防止单粒子反向散射，为基于自旋的电子学和计算开辟了新途径。但是，还必须考虑电子间库仑斥力的影响，因为两粒子的散射不受拓扑保护的阻碍，并且可能强烈影响边缘态电导。在这里，我们探索了电子相关性对SiC（0001）上独特的量子自旋霍尔材料铋的高度局限边缘状态的影响（参考 ¹）。利用具有可访问的单层基板系统的优势，我们使用STM / STS可视化边缘通道的接近完美的一维限制，并仔细研究了它们在费米能级下抑制的状态密度。根据观察到的光谱行为及其随能量和温度的普遍标度，我们证明了与（螺旋）Tomonaga–Luttinger液体的对应关系。特别地，所提取的相互作用参数K与温度的基本问题直接相关，在该温度下，量化的电导率（量子自旋霍尔材料的特征）将被相关性²所掩盖。