Mapping Electron Flow Around Sharp Bends Can Lead to the Development of Nanoscale Devices Inspired by Airplane Wings

For almost 80 years, it has been known that electrons tend to heat up when they travel around bends because their flow lines get squished locally. No attempt has been made to measure the heat for which flow line imaging is first needed.

Understanding Electron Flow Around Bends

At the University of California, Riverside, a research team led by physics and astronomy professor Nathaniel M. Gabor in imaging streamlines of electric current by designing an electrofoil. This new type of device allows the contortion, compression, and expansion of streamlines of electric currents in the same way that airflow is contorted, compressed, and expanded by airplane wings.

Electric charge moves in the same manner that air flows over the surface of an airplane wing. Visualizing airflow using streams of smoke or steam in a wind tunnel is easy, but imaging the streamlines of electric currents is much more difficult.

Electrons heat up when they gain kinetic energy, ultimately heating the material around them like the wires that can risk melting. When a computer gets a heat spike, the circuits may die. This is why computers shut off when they overheat since the circuits must be protected from getting damaged by all the heat dissipating in the metals.

In their experiment, Gabor and his team developed the first images of photocurrent streamlines through a working device by combining laser imaging with novel light-sensitive devices. As Gabor described, understanding the flow of electrons allows experts to prevent deleterious effects such as the heating up of the circuit. Scientists can assess exactly where and how the electrons are flowing with their newly discovered technique. This can give them a powerful tool for visualizing, characterizing, and measuring charge flow in optoelectronic devices.

Taking Flight at the Nanoscale

After successfully visualizing electron flow in sharp bends, the researchers designed the electrofoils as little wing shapes in nanoscale devices. This makes the electrons flow around the devices as air molecules flow around an airplane wing.

The experts wanted a shape that could give them different turning rates, like something with a continuous curvature. They took inspiration from airplane wings as they possess a gradual curve.

The current was forced to flow around the electrofoil, providing different light angles. More compression of the flow lines results from a sharper angle. In most materials, the team observes that electrons behave like liquids. Because of this, they did not design devices based on electrical resistance but adopted an approach with plumbing and planned pipelines for electrons to flow through.

Meanwhile, a laser beam was directed on the yttrium iron garnet (YIG) to generate a photocurrent in a desired direction, using the laser as a local heat source. This results in the photo-Nernst effect generating the photocurrent whose movement is controlled by the external magnetic field.

Tracking photocurrent streamlines in quantum optoelectronic devices using direct imaging is still challenging in understanding exotic device behavior. The team's study shows the robustness of photocurrent streamline microscopy as a new experimental tool in imaging a photocurrent in quantum materials.