In a surprising twist, scientists studying a special quantum material have discovered that it naturally forms one of the thinnest semiconductor junctions ever recorded—just 3.3 nanometers thick.
That’s about 25,000 times thinner than a sheet of paper.
This unexpected finding could lead to ultra-miniature electronics and advance the field of quantum technology.
Researchers from the University of Chicago’s Pritzker School of Molecular Engineering and Pennsylvania State University were originally exploring the properties of a material called MnBi₆Te₁₀.
This material belongs to a class known as topological insulators—materials that conduct electricity along their edges without resistance, making them prime candidates for future quantum computers and super-efficient electronics.
To enhance its properties, the scientists had carefully adjusted the chemical composition of MnBi₆Te₁₀ by adding antimony, expecting the result to be a charge-neutral material with evenly distributed electrons.
On the surface, everything appeared as planned. Basic electrical tests showed the material was indeed balanced overall.
But when the researchers examined it more closely using an advanced method called time- and angle-resolved photoemission spectroscopy (trARPES), they made a surprising discovery.
This technique uses fast laser pulses to study how electrons behave in real time. The team found that within each ultra-thin layer of the material’s crystal structure, the electrons were not evenly spread out.
Some areas had an excess of electrons, while others had fewer. This created small, built-in electric fields throughout the crystal—similar to what you’d find in a manufactured semiconductor junction.
This type of junction, called a p-n junction, is a crucial component in most modern electronics, including smartphones, computers, and solar panels. It works by allowing electric current to flow in a controlled way.
What makes this discovery remarkable is that these p-n junctions appeared naturally within the material, without any external engineering.
“This was a big surprise,” said Assistant Professor Shuolong Yang, who led the research. “We weren’t trying to make this junction, but the material made one on its own, and it’s one of the thinnest we’ve ever seen.”
The study’s lead author, graduate student Khanh Duy Nguyen, explained that while this uneven distribution of electrons could be a setback for some quantum applications—which require a uniform charge distribution—it also reveals a new and valuable property of the material.
Even more exciting, these tiny natural p-n junctions respond strongly to light. This makes them potential building blocks for future technologies such as spintronics, which use an electron’s magnetic spin instead of its electric charge to store and process data. Spintronics could lead to faster, smaller, and more energy-efficient devices.
The researchers believe that adding antimony to MnBi₆Te₁₀ may have caused some of the atoms in the material to swap places, disturbing the electron balance and triggering the formation of the junctions.
They are now working on refining the way they make thin films of the material, which could help them better control its properties—either to preserve the quantum behavior they originally sought, or to amplify the natural formation of p-n junctions for electronic use.
“This discovery shows how valuable basic scientific research can be,” said Yang. “We started out aiming for one goal, and we found something totally unexpected—and full of new possibilities.”
Source: University of Chicago.
