Shape of electrons is revealed for the first time in big quantum leap

For the first time, researchers have measured the shape of an electron as it moves through a solid. This major achievement in quantum physics promises to shed light on how electrons behave inside different materials and could inspire new technological advancements.

Riccardo Comin, MIT’s Class of 1947 Career Development Associate Professor of Physics, led the work in collaboration with other institutions. Their findings were published in Nature Physics.

"Think about an electron as moving through a periodic crystal, like a house," Comin explained. "Until now, we knew the energy and velocity of electrons, but not the details of their ‘crystal shape.’"

The team used a technique called angle-resolved photoemission spectroscopy (ARPES) to record details about how electrons behaved as light hit them. ARPES helped them pin down a previously elusive property of electrons, which holds the key to better understanding their geometry.

In every-day life, we talk about an electron’s energy or velocity. Geometry, on the other hand, points to the patterns or forms that electron waves can take when arranged in a solid. Previous observations of electron geometry were limited to simple or quirky one-dimensional systems.

Now, the team measured this geometric effect in a class of materials called kagome metals. Kagome metals are named for a repeating pattern of atoms that resembles a series of interlocking triangles. This lattice structure can influence how electrons navigate and share energy.

Physicsists have long been interested in kagome metals because they host behaviors that aren’t common in many other materials. Observing the geometry inside them could explain why electrons in these metals sometimes align in peculiar ways that set off advanced superconductivity or other strange effects.

This breakthrough follows years of theoretical predictions about quantum geometry. Until now, it was unclear whether these theoretical constructs describing wave functions had real, measurable consequences.

The study was a partnership among institutions spanning different parts of the world, bringing together theoretical and experimental backgrounds. Their collective expertise helped design, synthesize, and measure the electronic structure of a kagome metal.

Comin emphasizes that this is just the beginning. Many other materials have more complex and interesting structures. He imagines a future where scientists target exotic materials that exhibit other patterns or new behaviors.

"What we have right now is a blueprint for obtaining some completely new information that couldn’t be obtained before," Comin says.