Vanadium dioxide (VO2) is capable of “remembering” the full history of past external stimuli, according to researchers at École Polytechnique Fédérale de Lausanne (EPFL).
Vanadium dioxide is the first substance found by EPFL researchers that possess this feature.
The findings were published today in the journal Nature.
During his research on phase transitions in vanadium dioxide, Mohammad Samizadeh Nikoo, a Ph.D. student at EPFL’s Power and Wide-band-gap Electronics Research Laboratory (PowerLab), made an unintentional finding (VO2).
According to the study, when relaxed at room temperature, VO2 has an insulating phase and undergoes a steep insulator-to-metal transition at 68 °C, where its lattice structure changes.
VO2 has volatile properties under typical settings. “The material reverts to the insulating state immediately once the excitation is removed,” said Mohammad Samizadeh Nikoo.
The revelation came as a surprise.
Samizadeh Nikoo experimented by passing an electric current through a VO2 sample. “The current passed through the material, following a course until it exited on the other side,” he explained.
Following the current passed in the first application, the material returned to its original state, and after Samizadeh Nikoo’s second application, the substance began to exhibit “remembering” characteristics.
“The VO2 seems to remember the first phase transition and predict the next,” reveals PowerLab director Prof. Elison Mattioli. “This type of memory effect surprised us, and it has nothing to do with electronic states but rather with the physical structure of the material. It is a remarkable discovery because no other material behaves in this manner.”
The researchers discovered that VO2 can remember its most recent external input for up to three hours.
“The memory effect could last for several days,” Prof. Mattioliremember says, “but we don’t have the equipment to measure it right now.”
The significance of the memory impact
The discovery made by the study team is thought to be highly significant. The memory effect discloses a previously unknown feature of vanadium dioxide.
Engineers rely on memory to complete a wide range of computations, and materials that can improve the calculation process by increasing capacity, speed, and compactness are in high demand.