Engineers at Stanford University have found that strontium titanate, a common material, exhibits superior optical and mechanical properties at cryogenic temperatures near absolute zero. This breakthrough could advance quantum computing, lasers, and space exploration by enabling high-performance devices in extreme cold. The findings, published in Science, highlight the material's nonlinear and piezoelectric capabilities that outperform existing alternatives.
Strontium titanate (STO) has long been overlooked as an inexpensive, abundant substance, often used as a diamond substitute in jewelry or a substrate for other materials. However, new research from Stanford University reveals its exceptional performance under cryogenic conditions, defying expectations for most materials that weaken near absolute zero.
In a study published in Science on November 8, 2025 (volume 390, issue 6771, page 394; DOI: 10.1126/science.adx8657), researchers tested STO at 5 Kelvin (-450°F). Its nonlinear optical response proved 20 times greater than lithium niobate, the leading nonlinear optical material, and nearly triple that of barium titanate, the prior cryogenic benchmark. "Strontium titanate has electro-optic effects 40 times stronger than the most-used electro-optic material today. But it also works at cryogenic temperatures, which is beneficial for building quantum transducers and switches that are current bottlenecks in quantum technologies," said senior author Jelena Vuckovic, professor of electrical engineering at Stanford.
The material's electro-optic effects allow dramatic shifts in light's frequency, intensity, phase, and direction when an electric field is applied. As a piezoelectric substance, STO expands and contracts in response to electric fields, making it suitable for electromechanical components in space vacuums or rocket fuel systems. "At low temperature, not only is strontium titanate the most electrically tunable optical material we know of, but it's also the most piezoelectrically tunable material," noted co-first author Christopher Anderson, now at the University of Illinois, Urbana-Champaign.
To enhance tunability, the team replaced oxygen atoms with heavier isotopes, adding two neutrons to exactly 33 percent of them, boosting performance by a factor of four and approaching quantum criticality. "STO is not particularly special. It's not rare. It's not expensive," added co-first author Giovanni Scuri, a postdoctoral scholar in Vuckovic's lab.
Funded partly by Samsung Electronics and Google's quantum computing division, the research paves the way for wafer-scale fabrication of cryogenic devices like laser-based quantum switches. Contributors include Aaron Chan and Lu Li from the University of Michigan, along with Stanford's Sungjun Eun, Alexander D. White, Geun Ho Ahn, Amir Safavi-Naeini, Kasper Van Gasse, and Christine Jilly from Stanford Nano Shared Facilities. The team aims to develop fully functional devices based on STO's properties.