Molecular dynamics simulation of the lithium niobate under a time varying electric field.

A new efficient way to pump or extract heat using crystals has been discovered by researchers at the Carnegie Institution. The crystals can pump or extract heat at nanoscales and may have applications in computer chips to prevent overheating, currently a major limit to higher computer speeds.

The researchers, whose findings are published in Physical Review Letters, performed simulations on ferroelectric crystals- materials that have electrical polarization which can be reversed in the presence of an electric field. The team found that introducing the electric field caused a giant temperature change in the material, dubbed the electrocaloric effect, to a paraelectric state.

“The electrocaloric effect pumps heat through changing temperature by way of an applied electric field,” explained Ronald Cohen, staff scientist at Carnegie’s Geophysical Laboratory.

The researchers followed the behaviour of atoms in the ferroelectric lithium niobate (a compound with a low transition temperature) and investigated the effect of temperature and a time-varying electric field.

“The effect has been known since the 1930s but has not been exploited because people were using materials with high transition temperatures (the temperature at which a material changes state from ferroelectric to paraelectric). We found that the effect is larger if the ambient temperature is well above the transition temperature So if you want to use it at room temperature, for example, the transition temperature should be below room temperature,” Cohen told Laboratory News.

Ferroelectric crystals become paraelectric, meaning they have no polarization under zero electric field above their transition temperature.

Meriom Rose who conducted the research with Cohen while working as a high school intern at the Carnegie Institution said: “Lithium niobate had not been studied before like this. We were pretty surprised to see such a huge temperature change.”