Tunnelling is one of the most fundamental manifestations of quantum mechanics. The recent advent of lightwave-driven scanning tunnelling microscopy has revolutionized ultrafast nanoscience by directly resolving electron tunnelling in electrically conducting samples on the relevant ultrashort length- and timescales. Here, we introduce a complementary approach based on terahertz near-field microscopy to perform ultrafast nano-videography of tunnelling processes even in insulators. The central idea is to probe the evolution of the local polarizability of electron–hole pairs with evanescent terahertz fields, which we detect with subcycle temporal resolution. In a proof of concept, we resolve femtosecond interlayer transport in van der Waals heterobilayers and reveal pronounced variations of the local formation and annihilation of interlayer excitons on deeply subwavelength, nanometre scales. Such contact-free nanoscopy of tunnelling-induced dynamics should be universally applicable to conducting and non-conducting samples and reveal how ultrafast transport processes shape functionalities in a wide range of condensed matter systems.

隧道效应是量子力学最基本的表现之一。最近出现的光波驱动扫描隧道显微镜通过在相关的超短长度和时间尺度上直接解析导电样品中的电子隧道效应，彻底改变了超快纳米科学。在这里，我们介绍了一种基于太赫兹近场显微镜的补充方法，即使在绝缘体中也能对隧道过程进行超快纳米摄像。中心思想是探索具有倏逝太赫兹场的电子-空穴对的局部极化率的演变，我们用亚周期时间分辨率检测到。在概念验证中，我们解决了范德华异质双层中的飞秒层间传输，并揭示了在深亚波长纳米尺度上层间激子的局部形成和湮灭的显着变化。这种隧穿诱导动力学的非接触式纳米技术应该普遍适用于导电和非导电样品，并揭示超快传输过程如何在各种凝聚态系统中塑造功能。