Harvard physicists reported on Mar. 19 new insights into the uneven performance of a promising superconductor, using an innovative technique that allows for detailed study of materials under high pressure.
The research addresses a longstanding challenge in condensed matter physics: creating superconductors that operate at room temperature and transmit electricity without loss. Superconductors have the potential to revolutionize energy transmission and various technologies by eliminating resistance, but practical applications have been limited by the need for extremely cold temperatures.
In a recent paper published in Nature, the team led by Norman Yao, professor of physics at Harvard University, and Chris Laumann, associate professor of physics at Boston University, described how they added quantum sensors to a device originally developed by Nobel laureate Percy Bridgman. This adaptation enables researchers to ask new questions about materials under extreme conditions. “We can ask questions at high pressure that we could never ask before,” said Yao. “And the question that we’ve been getting the most from our colleagues is: Can you measure our rock too?”
The team’s approach involves using diamond anvils embedded with nitrogen vacancy centers—defects created by bombarding diamonds with ions and heating them—to detect magnetic and electric fields within samples subjected to pressures above 100 gigapascals. This setup allows scientists to observe changes in local magnetic fields around nickelate samples, providing early evidence of superconductivity through what is known as the Meissner effect. “This nitrogen vacancy measurement is able to see superconductivity on significantly smaller-length scales and long before conventional methods that are based upon resistance,” said Srinivas Mandyam, co-lead author and doctoral student in physics.
By mapping samples at micron scale, researchers found that superconductivity first appears in localized regions near critical pressure points and expands as more pressure is applied. The study also revealed that shear stresses can limit superconductivity within these materials. According to Yao, “The tools that we’ve been developing as a group are quite special because you can really image functionality under pressure and determine where exactly the material acts as a superconductor.” These findings suggest that each sample should be viewed as a collection of small regions with different behaviors rather than as uniform materials.
Laumann said this technology will help researchers better explore various types of superconductive materials discovered so far: “It’s like if a tree falls in the woods and nobody’s there to hear it, does it make a sound? If nobody is there to tell you, it’s just not something you can see or discuss. The fact that we can now make these local measurements opens up a whole new range of questions.”
