This is the first know material that possesses this ability but others could exist. PhD student Mohammad Samizadeh Nikoo was researching phase transitions in vanadium dioxide – specifically, how long it takes the material to transition from one state to another. When the material reaches 68 degrees Celsius, it undergoes a steep insulator-to-metal transition. His tests involved applying an electric current to a material, which heats it up (and causes it to change states) as it moves from one side to the other. Once the current passes, the material cools and returns to its original state.
After recording hundreds of measurements, Nikoo picked up on a memory effect in the material’s structure. When applying a second current pulse to the material, he noticed that the time it took to change state was directly linked to its history. “The VO2 seemed to ‘remember’ the first phase transition and anticipate the next,” said Professor Elison Matioli, who heads the lab where the discovery was made. “We didn’t expect to see this kind of memory effect, and it has nothing to do with electronic states but rather with the physical structure of the material,” the professor added. Further testing revealed the material can remember its most recent stimuli for up to three hours. The memory effect may even persist for longer - perhaps even for several days - but the team does not have the instruments needed to make those measurements. The publication notes that the discovery seemingly replicates what happens in the brain, with the VO2 switches acting like neurons. “No other material behaves in this way,” said Matioli. A material that could enhance the performance of calculations through greater capacity, miniaturization and speed would be a boom for electronics makers, and VO2 could do just that. It also stands apart from traditional materials that store data as binary information based on the manipulation of an electronic state. The team’s work has been published in the journal Nature. Image credit: Chokniti Khongchum
