Liquid graphene electrons flow 'like a wave through water' producing electric currents

The wonder material graphene has provided scientists with even more reasons to be optimistic about its applications, as they find its electrons moving "like a wave through water." This liquid motion means that the heat produced gives rise to electric currents in graphene, as the electrons act as both negative and positively charged.

The research, published in the journal Science, describes the first time a metal's electrons have been seen moving as a liquid. This movement ultimately makes life a lot easier for scientists who aim to make electric currents from metal.

"Converting thermal energy into electric currents and vice versa is notoriously hard with ordinary materials," said Andrew Lucas, co-author of the research from Harvard University. "But, in principle, with a clean sample of graphene there may be no limit to how good a device you could make."

The scientists also discussed how the electrons moved incredibly quickly in the absence of heat – smashing into each other roughly 10 trillion times every second.

What is graphene?

Graphene is a man-made metal that has been touted as a 'wonder material', as it is super-strong, super-hard and super-conductive. It is stronger than steel, harder than even diamond and is a better conductor than copper.

It is just one-atom thick, making it a two-dimensional sheet as opposed to a block, and scientists have suggested that it could one day be used for creating fuel-free spacecraft and even artificial skin.

However, there are still fundamental physics questions that remain unanswered about the metal, which was discovered in 2004. Scientists have now unlocked the mystery to its electrons, however, and have discovered they move unlike any other metal known to mankind.

"Like a wave through water"

They came to their conclusion by putting the graphene under intense heat, and watching the electrons moving about randomly by themselves, generating tiny vibrations. Just like a mobile phone, each vibration made a slight noise, which the researchers measured to investigate how much heat was being carried by the electrons – and therefore, discover how these electrons move.

The researchers found that the movement of its electrons mimicked that of flowing water. Compared to the usual observations in metals, which includes single electrons moving independently, graphene's electrons act in unison and all move together like a ripple in a puddle.

"Instead of watching how a single particle was affected by an electric or thermal force, we could see the conserved energy as it flowed across many particles, like a wave through water," said Jesse Crossno, a researcher on the study.

This means that, in principle, there is no end to the amount of thermal energy that graphene can convert into electric currents, a process, which until now, had scientists believing was incredibly difficult.

Ferocious electrons at room temperature

The researchers also noted that when the graphene sheet was sitting at room temperature, the electrons move as if they are crossing a continuous four-way road junction − without traffic lights. Whilst moving at more than 2.2m miles per hour, this naturally meant that collisions occurred at 600 trillion times every minute.

This violent movement has also never been seen in any other metal before.

Using graphene as a model

The way that the electrons move across the graphene sheet has been likened to high-energy systems, including black holes and supernovas. It combines separate laws of physics in the exact same way as these systems, including relativistic physics (the science of galaxies) and quantum mechanics (tiny electrons).

With that in mind, the researchers hope to use graphene in the future as a way to model more high-energy systems.

"Physics we discovered by studying black holes and string theory, we're seeing in graphene," said Lucas. "This is the first model system of relativistic hydrodynamics in a metal."