Ania Jayich and the Quantum Sensing and Imaging Group at UC Santa Barbara have developed new sensor technology capable of nanometer-scale spatial resolution and exquisite sensitivity.
Image Credit: Quantum Sensing and Imaging Group at UC Santa Barbara (Via PhysOrg)
“This is the first tool of its kind. It operates from room temperature down to low temperatures where a lot of interesting physics happens,” Jayich, UCSB’s Bruker Endowed Chair in Science and Engineering and associate director of the campus’s Materials Research Lab, told PhysOrg. “When thermal energy is low enough, the effects of electron interactions, for instance, become observable, leading to new phases of matter. And we can now probe these with unprecedented spatial resolution.”
PhysOrg describes the single-spin quantum sensor as resembling a toothbrush. Each bristle contains a single, solid nanofabricated diamond crystal with a special defect, a nitrogen-vacancy (NV) center, located at the tip. Two adjacent atoms are absent in the diamond’s carbon lattice, as one space has been filled with a nitrogen atom, allowing for the sensing of specific material properties, particularly magnetism. Indeed, Jayich and team chose to image a well-studied superconducting material containing magnetic structures known as vortices, or localized regions of magnetic flux. Using the sensor, the scientists were able to image individual vortices.
“Our tool is a quantum sensor because it relies on the bizarreness of quantum mechanics,” Jayich explained. “We put the NV defect into a quantum superposition where it can be one state or another—we don’t know—and then we let the system evolve in the presence of a field and measure it. This superposition uncertainty is what allows that measurement to occur.”
The Quantum Sensing and Imaging Group at UC Santa Barbara is now imaging skyrmions—quasiparticles with magnetic vortex-like configurations—with future data storage and spintronic technologies in mind.
Image Credit: Quantum Sensing and Imaging Group at UC Santa Barbara (Via PhysOrg)
“This tool will aid in understanding the nature and the strength of interactions in materials that then give rise to interesting new states and phases of matter, which are interesting from a fundamental physics perspective but also for technology,” she added.
Commenting on the above, Patrick Gill, Principal Research Scientist at Rambus, says the new sensor, which comprises bristles with solid nanofabricated diamond crystals, brings to mind the four Cs of diamond quality: cut, clarity, color and carat.
“It’s [interesting] how you can think of diamonds as giant single molecules made mostly of covalently-linked carbon atoms,” he said. “With Ania Jayich’s group at UC Santa Barbara, the c for ‘color’ could be replaced by a ‘q’ for quantum magnetometer. That’s because a specific diamond defect called a ‘nitrogen vacancy,’ which causes a yellow color in bulk diamond, can also act as a very sensitive magnetometer. “
As Gill notes, single NV defects will fluoresce when excited by green 532nm light in a way that’s extremely sensitive to the local magnetic field.
“[As described above], making a comb of diamond needles with a single NV defect at the tip of each one [allows scientists] to scan patches of material to image even weak magnetic features on length scales much smaller than a single micron,” he concluded. “The publication [authored by the UC team] shows several impressive images of magnetic features of a hard drive and magnetic vortices in an iron pnictide superconductor, illustrating how the technique can work both at ambient and cryogenic temperatures. The next time I see a diamond that’s a little yellow, rather than reflecting on the implications of the rock as a gemstone, I’ll think about how it could be used to probe tiny and delicate magnetic phenomena through a quantum effect.”
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