Reviewed by Lexie CornerOct 3 2024
Researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) and the U.S. Department of Energy's (DOE) Argonne National Laboratory have proposed a new form of memory. This approach involves transferring optical data from a rare earth element embedded in a solid material to a nearby quantum defect. Their exploration of how this technology could work was published in Physical Review Research.
Researchers at Argonne and the University of Chicago combined classical physics with quantum modeling to show how rare-earth elements (red dots) and defects (blue dots) within solids can interact to store optically encoded classical data. Image Credit: The University of Chicago.
With over two quintillion bytes of new data generated daily in the digital world, existing storage technologies are quickly reaching their limits. Optical memory devices, which read and write data using light, offer the potential for faster, more reliable, and energy-efficient storage solutions.
We worked out the basic physics behind how the transfer of energy between defects could underlie an incredibly efficient optical storage method. This research illustrates the importance of exploring first-principles and quantum mechanical theories to illuminate new, emerging technologies.
Giulia Galli, Senior Scientist, Argonne National Laboratory
The diffraction limit of light limits the majority of optical memory storage technologies created in the past, such as CDs and DVDs. The wavelength of the laser used to write and read the data cannot be smaller than a single data point.
In the new study, researchers proposed using multiple rare-earth emitters embedded in the material to increase optical storage density. These emitters could utilize wavelength multiplexing—employing slightly different light wavelengths—to store more data within the same area.
To explore the feasibility of this approach, the team, led by Galli, first investigated the physics requirements for efficient and dense optical storage. They developed models of a theoretical material with rare-earth emitter atoms dispersed throughout. These atoms absorb and re-emit light at specific, narrow wavelengths. The researchers demonstrated how nearby quantum defects could absorb the re-emitted light at these precise wavelengths.
By combining quantum mechanical theories of light propagation at the nanometer scale with first-principles electronic structure theories to map defect states, the study predicted how energy transfers between the emitters and defects. These innovative models helped the team better understand the energy transfer dynamics and how the defects store captured energy.
We wanted to develop the necessary theory to predict how energy transfer between emitters and defects work. That theory then allowed us to figure out the design rules for potentially developing new optical memories.
Swarnabha Chattaraj, Postdoctoral Research Fellow, Argonne National Laboratory
Although the typical interaction between light and quantum defects in solid materials is well understood, the behavior of these defects when exposed to light from an extremely close source—such as narrow-band rare-earth emitters embedded only a few nanometers away—has not yet been thoroughly investigated by scientists.
This kind of near-field energy transfer is thought to follow different symmetry rules than more commonly known far-field processes.
Supratik Guha, Senior Advisor, Physical Sciences and Engineering Directorate and PME Professor, Argonne National Laboratory
The team discovered that the quantum defects transitioned from their ground state and flipped their spin state when they absorbed energy from the narrow band emitted by the surrounding atoms. Since reversing this spin state transition is highly challenging, these defects could store data for extended periods.
Additionally, the use of narrow-band rare-earth emitters and the small size of the quantum defects allows for denser data storage than traditional optical methods.
Chattaraj concluded, “To start applying this to developing optical memory, we still need to answer additional basic questions about how long this excited state remains and how we read out the data. But understanding this near-field energy transfer process is a huge first step.”
The study was supported by the DOE Office of Science for microelectronics research.
Journal Reference:
Chattaraj, S. et. al. (2024) First-principles investigation of near-field energy transfer between localized quantum emitters in solids. Physical Review Research. doi.org/10.1103/PhysRevResearch.6.033170