For a century, physicists have treated most solid materials as forgetful — reset them, and they behave the same way every time. A team at ISTA has now found a class of quantum materials that seems to break that rule.
The finding, published this month in Nature Physics, describes an unexpected phase transition observed at temperatures close to absolute zero. When the researchers cooled a thin film of a topological insulator and swept a magnetic field across it, the material's electrical response depended not only on the field's current value but on where it had just been — a signature usually associated with magnets, not with this class of quantum matter.
A memory where none was expected
"We were looking for something else entirely," says Professor Mira Maric, who leads the group. "The hysteresis loop appeared, disappeared when we changed the sample, and came back. It took us a year to convince ourselves it was real."
"The materials we call inert may be quietly keeping records."
What makes the result surprising is that the topological states involved were thought to be "protected" — robust against exactly the kind of disturbance that would leave a lasting imprint. The team's measurements suggest that protection has limits, and that within those limits the material can hold information in a physically stable way.
Why it matters for data storage
If the effect can be controlled, it points toward a new way to store information — one that could be faster and use less energy than the magnetic storage in today's hard drives. That application is years away, the team cautions. The immediate value is to theory: no existing model predicts the behaviour they measured.
The group is now working with ISTA's Nanofabrication Facility to build cleaner samples and test whether the memory effect survives at higher temperatures — the crucial step toward anything practical.