image: ‘An artistic schematic of the investigation of a single spin in hexagonal boron nitride via confocal microscopy, showing the objective lens focussing the laser light on the sample with a coil for spin microwave control.’
Credit: Credit: Eleanor Nichols, Cavendish Laboratory
For the first time, scientists at the Cavendish Laboratory have found that a single ‘atomic defect’ in a thin material, Hexagonal Boron Nitride (hBN), exhibits spin coherence under ambient conditions, and that these spins can be controlled with light. Spin coherence refers to an electronic spin being capable of retaining quantum information over time. The discovery is significant because materials that can host quantum properties under ambient conditions is quite rare.
The findings published in Nature Materials, further confirm that the accessible spin coherence at room temperature is longer than the researchers initially imagined it could be. “The results show that once we write a certain quantum state onto the spin of these electrons, this information is stored for ~1 millionth of a second, making this system a very promising platform for quantum applications,” said Carmem M. Gilardoni, co-author of the paper and Rubicon postdoctoral fellow at the Cavendish Laboratory.
“This may seem short, but the interesting thing is that this system does not require special conditions – it can store the spin quantum state even at room temperature and with no requirement for large magnets.”
Hexagonal Boron Nitride (hBN) is an ultra-thin material made up of stacked one-atom-thick layers, kind of like sheets of paper. These layers are held together by forces between molecules. But sometimes, there are ‘atomic defects’ within these layers, similar to a crystal with molecules trapped inside it. These defects can absorb and emit light in the visible range with well-defined optical transitions, and they can act as local traps for electrons. Because of these ‘atomic defects’ within hBN, scientists can now study how these trapped electrons behave. They can study the spin property, which allows electrons to interact with magnetic fields. What's truly exciting is that researchers can control and manipulate the electron spins using light within these defects at room temperature.
This finding paves the way for future technological applications particularly in sensing technology.
However, since this is the first time anyone has reported the spin coherence of the system, there is a lot to investigate before it is mature enough for technological applications. The scientists are still figuring out how to make these defects even better and more reliable. They are currently probing how far we can extend the spin storage time, and whether we can optimise the system and material parameters that are important for quantum-technological applications, such as defect stability over time and the quality of the light emitted by this defect.
“Working with this system has highlighted to us the power of the fundamental investigation of materials. As for the hBN system, as a field we can harness excited state dynamics in other new material platforms for use in future quantum technologies,” said Dr. Hannah Stern, first author of the paper, who conducted this research at the Cavendish Laboratory and is now a Royal Society University Research Fellow and Lecturer at University of Manchester.
In future the researchers are looking at developing the system further, exploring many different directions from quantum sensors to secure communications.
“Each new promising system will broaden the toolkit of available materials, and every new step in this direction will advance the scalable implementation of quantum technologies. These results substantiate the promise of layered materials towards these goals,” concluded Professor Mete Atatüre, Head of the Cavendish Laboratory, who led the project.
Journal
Nature Materials