A simple chemical tweak could supercharge quantum computers

Researchers at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) and West Virginia University have now demonstrated a practical way to bring these materials within reach. By slightly adjusting a chemical formula, they were able to alter how large numbers of electrons interact inside the material, guiding it into a topological superconducting state.

The team focused on ultra thin films made from two elements, tellurium and selenium. By carefully changing the proportion of these elements, they discovered they could push the material from one quantum phase to another, including the sought after topological superconductor phase.

Their results, published in Nature Communications, show that modifying the tellurium to selenium ratio changes how strongly electrons influence one another. These electron correlations act like a fine tuning mechanism, allowing scientists to deliberately engineer unusual quantum states.

"We can tune this correlation effect like a dial," said Haoran Lin, a UChicago PME graduate student and first author of the new work. "If the correlations are too strong, electrons get frozen in place. If they're too weak, the material loses its special topological properties. But at just the right level, you get a topological superconductor."

"This opens up a new direction for quantum materials research," said Shuolong Yang, Assistant Professor of Molecular Engineering and senior author of the new work. "We've developed a powerful tool for designing the kind of materials that next-generation quantum computers will need."

Iron Telluride Selenide and Competing Quantum Effects

The material at the center of the study, iron telluride selenide, was discovered relatively recently and is known for combining superconductivity with unusual topological behavior.

"This is a unique material because it brings together all the essential ingredients one would hope for in a platform for topological superconductivity: superconductivity itself, strong spin-orbit coupling, and pronounced electronic correlations," said Subhasish Mandal, an assistant professor of physics at West Virginia University and an author on the new paper. "This combination makes it an ideal system in which to explore how different quantum effects interact and compete."

Previously, scientists produced this material in bulk crystal form and observed intriguing quantum states. However, bulk crystals are challenging to manipulate, and their chemical makeup can vary from one region to another, making consistent results harder to achieve.

Thin Films for Stable Quantum Devices

Topological superconductors are especially attractive for quantum technologies because their topological states are naturally stable and less vulnerable to the noise that disrupts most quantum systems.

The ultra thin films developed by Yang's group offer several advantages over other topological superconductor candidates. They operate at temperatures as high as 13 Kelvin, compared with about 1 Kelvin for aluminum based platforms. This higher operating temperature makes them easier to cool using standard liquid helium systems. In addition, thin films provide greater uniformity and are more compatible with modern device fabrication techniques than bulk crystals.

"If you're trying to use this material for a real application, you need to be able to grow it in a thin film instead of trying to exfoliate layers off of a rock that might not have a consistent composition throughout," explained Lin.

Several research teams are already working with Yang's group to pattern these films and build prototype quantum devices. At the same time, the researchers continue to investigate other characteristics of thin film iron telluride selenide to better understand its potential for next generation quantum computing.