Image Credit: Norman Yao/Berkeley Lab; Ella Marushchenko
A team of scientists from Berkley Lab and UC Berkley has manipulated the atomic flaws of diamond anvil cells by turning them into miniature quantum sensors. Diamond anvil cells enable the compression of small sub-millimeter-sized materials which can be used to recreate the conditions deep inside planets as well as chemical reactions sparked by immense pressure.
Thus, by synthesizing complex chemical reactions or a simulation of the Earth’s mantle, scientists can witness the ways in which high-pressure phenomena acts. Additionally, these devices mean that the changes in physical, chemical, and electronic properties of matter can be observed across a diverse landscape of high-pressure events. This is useful because it allows scientists to enhance their understanding of how the properties of matter – such as stability, conductivity, and electromagnetism – change under extreme pressure. In turn, they can then develop new high-performance, robust materials.
The issue so far has been finding a device that can accurately measure these properties with a sensor that can withstand the substantial pressures found within a diamond anvil cell. In their search for finding a solution, the Berkley Lab and UC Berkley team have refined their existing methodologies to develop their ingenious solution: by turning the atomic flaws of the diamond anvil cells into quantum sensors. Thereby creating a sensor capable of conducting experiments and measuring phenomena inaccessible to traditional devices.
From Atomic Flaw to Quantum Sensor
Published in the journal Science, the Berkley Lab and UC Berkley based team discuss how their findings could initiate further progress when developing new materials and chemical compounds atomically calibrated by high-pressure. Introducing the concept of using a nanoscale platform that integrates nitrogen-vacancy (NV) centers directly into the cutlet of the diamond anvil cells. When the impurity of a nitrogen atom becomes trapped it is held adjacent to an empty space where the atomic defect forms: a nitrogen-vacancy center.
This space is generated when the carbon atoms are knocked out of phase as they assemble in the traditional tetrahedral crystal structure. Scientists have been using these nitrogen-vacancy centers as tiny sensors for over a decade. Norman Yao, Faculty Scientist in Berkeley Lab's Materials Sciences Division and assistant professor of physics at UC Berkeley explains that they can then measure a wide range of events and phenomena such as, “the magnetism of a single protein”, “the electric field from a single electron” and “the temperature inside a living cell.”
So, by assembling a super-thin layer of nitrogen-vacancy centers inside of the diamond anvil cell they were able to create an image of the physics and events occurring inside the device. At just a few hundred atoms of thickness the layer of nitrogen-vacancy center sensors allowed the researchers to see how the sensors reacted to various small-scale alterations inside the diamond anvil cell.
Images of Diamond Anvil Cell Phenomena
Under the duress of light emitted by a laser the nitrogen-vacancy centers sensors radiate a bright red hue. By measuring the brightness of the glow, the team discovered that under pressure the even-surface of the diamond anvil would curve at its center. "They had known about this effect for decades but were accustomed to seeing it at 20 times the pressure, where you can see the curvature by eye," Yao said. "Remarkably, our diamond anvil sensor was able to detect this tiny curvature at even the lowest pressures."
Other phenomena included the transformation of an ethanol/methanol from a liquid into a solid as the diamond anvil cell morphed as the flat surface became broken and uneven.
This is a fundamentally new way to measure phase transitions in materials at high pressure, and we hope this can complement conventional methods that utilize powerful X-ray radiation from a synchrotron source.
Satcher Hsieh, Lead-author and Doctoral Researcher in Berkeley Lab's Materials Sciences Division and in the Yao Group at UC Berkeley
The team was also able to observe a magnetic “snapshot” of the pressure induced phase transition of iron and gadolinium. The researchers discovered that the NV center sensors can switch into different quantum magnetic states when subjected to magnetic fluctuations: like how a compass needle spins in different directions when influenced by a magnet.
Future Applications
Having mastered the assembly and insertion of nitrogen-vacancy centers into the diamond anvil cells the Berkley Labs and UC Berkley team aim to explore other applications for their quantum sensors. Soon, they hope to utilize the ability of the sensors to analyze magnetic behavior in certain superconducting materials. This has the potential for innovating energy transfer and storage of hybrid materials that conduct electricity at high pressures.
What’s more, is that these newly developed quantum sensors have the capacity to bridge scientific gaps between fields and have applications beyond the realm of physics. “What's most exciting to me is that this tool can help so many different scientific communities,” said Hsieh. “It's sprung up collaborations with groups ranging from high-pressure chemists to Martian paleomagnetists to quantum materials scientists.”
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