Technion Researchers Fuse Light Pulses with Scanning Tunneling Microscopy to Track Electron Motion

A collaborative team led by scientists at Israel's Technion has demonstrated a new technique that merges ultrafast laser pulses with a scanning tunneling microscope (STM), allowing them to steer and observe electron flow at the scale of individual atoms.

The breakthrough addresses a long‑standing challenge in condensed‑matter physics: visualising an electron as it traverses a material while simultaneously resolving the atomic landscape it inhabits. Traditional STM excels at mapping surface topography with sub‑angstrom precision, but its temporal resolution is limited to relatively slow scanning rates. Conversely, ultrafast laser spectroscopy can capture events that unfold in femtoseconds, yet it lacks the spatial granularity to pinpoint single‑atom features. By integrating the two approaches, the Technion team achieved both atomic‑scale spatial resolution and femtosecond‑scale temporal control.

In the experimental setup, a brief burst of light—lasting only a few tens of femtoseconds—illuminates the tip‑sample junction of the STM. The pulse temporarily modifies the electronic potential at the junction, effectively acting as a gate that can accelerate, decelerate, or redirect electrons tunnelling between the tip and the sample. The researchers then record the resulting tunnelling current, which reflects how the electron wave packet responded to the optical stimulus.

Initial measurements demonstrate that the method can modulate electron flow with a precision previously unattainable in a single instrument. The ability to launch, pause, and steer electrons on such short timescales opens a window onto fundamental processes such as charge transfer, surface reactions, and quantum coherence in nanostructures. Moreover, the technique provides a direct experimental platform for testing theoretical models of ultrafast electron dynamics that have so far been confined to simulations.

While the proof‑of‑concept experiment focused on simple metallic surfaces, the researchers note that the approach is readily adaptable to a variety of materials, including semiconductors, two‑dimensional crystals, and molecular assemblies. Extending the method to more complex systems could illuminate how electrons interact with lattice vibrations, defects, or magnetic textures, information that is critical for the design of next‑generation electronic and spintronic devices.

The development arrives at a time when the electronics industry is pushing toward ever‑smaller components and faster operation speeds. Understanding electron behaviour at the combined limits of space and time may inform strategies to minimise energy loss, mitigate heating, and harness quantum effects in future circuitry.

Looking ahead, the team plans to refine the synchronization between the laser pulses and the STM feedback loop, aiming to achieve even finer control over the timing of electron injection. They also intend to explore pump‑probe configurations that could map out the full temporal evolution of electron states after excitation. Such advances would cement the hybrid instrument as a versatile tool for both basic research and applied nanotechnology.