![]() Our measurements show that the vertical decay of the differential conductance is remarkably sensitive to lateral position and electronic orbital. THz-STS performed as a function of three-dimensional position above the GNR allows us to extract the differential conductance sampled by lightwave-driven tunnelling with ångström horizontal and sub-ångström vertical resolution. The small duty cycle of lightwave-driven tunnelling facilitates measurements at ultralow tip heights, where the GNR electronic wavefunctions feature far richer spatial structure than at conventional STM tip heights. Here, we investigate the promising material platform of atomically precise graphene nanoribbons 22 (GNRs) on the ångström scale with lightwave-driven terahertz scanning tunnelling microscopy (THz-STM) and spectroscopy (THz-STS). However, atomically resolved lightwave-driven spectroscopy is needed to realize this promise, and its demonstration remains outstanding. The natural next step is to bring these capabilities to bear on novel material systems to inform design and synthesis. Ultrafast fields can also operate in regimes inaccessible to conventional static STM fields, for example through lightwave-control of extreme tunnel currents 10, 11, 12, 16, 21. It has enabled femtosecond pump-probe experiments 8, 9, 13, 19, field-driven electroluminescence 20, and the application of atomic-scale ultrafast forces 15, 17. Lightwave-driven STM 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 opens another dimension: atomically resolved microscopy on ultrafast timescales. ![]() Scanning probe techniques that visualize orthogonal material properties on the atomic scale are also emerging, including electro- and photoluminescence STM 3, 4, electron spin resonance STM 5, and tip-enhanced Raman microscopy 6, 7. For example, combining scanning tunnelling microscopy (STM) and spectroscopy (STS) in differential conductance (d I/d V) maps reveals a sample’s local density of electronic states (LDOS), i.e., as a function of both position and energy. ![]() An equally important aspect is that scanning probe microscopy techniques can extract rich spectroscopic information at each spatial position. ![]() Yet, its success is not due to atomic spatial resolution alone. Scanning probe microscopy drives progress in materials science through atomically resolved real-space imaging of new compounds and nanostructures 1, 2. Lightwave-driven scanning tunnelling spectroscopy on the ångström scale paves the way for ultrafast measurements of wavefunction dynamics in atomically precise nanostructures and future optoelectronic devices based on locally tailored electronic properties. Tomographic imaging of their electron densities reveals vertical decays that depend sensitively on wavefunction and lateral position. ![]() Here, we utilize lightwave-driven terahertz scanning tunnelling microscopy and spectroscopy to investigate atomically precise seven-atom-wide armchair graphene nanoribbons on a gold surface at ultralow tip heights, unveiling highly localized wavefunctions that are inaccessible by conventional scanning tunnelling microscopy. It achieves simultaneous sub-ångström and sub-picosecond spatio-temporal resolution through ultrafast coherent control by single-cycle field transients that are coupled to the scanning probe tip from free space. Lightwave-driven scanning tunnelling microscopy is a promising technique towards this purpose. Atomically precise electronics operating at optical frequencies require tools that can characterize them on their intrinsic length and time scales to guide device design. ![]()
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