Electrons spiral with a purpose: A new platform decodes their selective spin

Yahoo

15-06-2025

By combining the principles of physics, chemistry, and biology, scientists have crafted a special programmable platform to explore one of the most puzzling quantum mysteries of our time: why electrons seem to choose sides when passing through certain twisted molecules.
This behavior, known as the chiral-induced spin selectivity (CISS) effect, has baffled researchers for over two decades. It shows up in biological processes like photosynthesis and cellular respiration, yet no one fully understands how or why it happens.
Now, researchers from the University of Pittsburgh have engineered an artificial, controllable system that can mimic the conditions under which this strange effect occurs. Their approach could reshape how we study quantum transport and might also help us design new materials for electronics, energy, and even medicine.
"The beauty of our approach is not that it mimics chemistry or biology exactly, but that it allows us to isolate and study individual processes that are relevant in chiral quantum transport," said François Damanet, a physicist and one of the members of the research team.
Back in the late 1990s, scientists Ron Naaman and David Waldeck made a surprising discovery. When electrons pass through films of chiral (twisted) molecules, how easily they can move is decided by their spin, which is a quantum property. Instead of a small noticeable effect, they saw spin-dependent changes as high as 20 percent, a result that stunned the scientific community.
Since then, the CISS effect has popped up in various biological systems, yet researchers haven't been able to pin down the exact mechanism behind it. This is because real biological molecules are complex. They're soft, flexible, constantly moving, and surrounded by water, all of which makes it nearly impossible to isolate the role of chirality alone.
That's where the new platform comes in. The researchers did not try to recreate biology. Instead, they built a clean, programmable playground for electrons. Using a technique developed in 2008, they worked with a special material made from layers of lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3).
By using a fine-tipped microscopic pen, they could draw paths where electrons can travel. To make those paths chiral, they introduced a clever twist: the probe not only moved in a wavy, serpentine pattern across the surface, but its voltage was also modulated up and down in sync. This combination created spiral-like channels that broke mirror symmetry, the key ingredient of chirality.
These artificial chiral waveguides weren't just pretty shapes. When electrons flowed through them, surprising quantum effects emerged. The team saw unusual conductance patterns and even observed electrons pairing up in ways that shouldn't be possible under strong magnetic fields.
Theoretical models suggested that the spiral geometry created a kind of engineered spin-orbit coupling, which locked the electrons' spin to their direction of motion, just like some theories had proposed for the CISS effect in molecules.
What makes this platform so powerful is that it's fully programmable. Researchers can change the shape, size, and strength of the chiral patterns, erase them, and write new ones, all on the same device. "We can systematically vary parameters like the pitch, amplitude, and coupling strength of chiral modulations—something impossible with fixed structures," Damanet said.
This new platform doesn't try to copy molecules atom-for-atom. Instead, it gives scientists something they've never had before: precise control. In biological systems, everything is messy—molecules wiggle, environments shift, and vibrations interfere with measurements.
However, on this programmable platform, each variable can be changed independently, allowing researchers to test exactly how chirality affects quantum transport. This could help settle long-standing debates about whether spin-orbit interactions, molecular vibrations, or other mechanisms drive the CISS effect.
While the system operates at ultra-cold temperatures and uses inorganic materials, it sets the stage for future hybrid setups that could combine these solid-state tools with real molecules.
The team is already exploring ways to pair their platform with organic materials or carbon nanotubes, and even to run experiments at higher temperatures. The goal isn't to replace biological studies, but to work alongside them, much like how wind tunnels help engineers test aircraft designs before real-world flights.
If successful, this approach could help scientists not only solve the CISS puzzle but also understand other complex quantum systems. It could inspire new materials for spintronics, where electron spin is used in computing, or guide the design of efficient catalysts and bio-inspired energy devices.
The study is published in the journal Science Advances.