The ‘atomic Lego set’ revealing electrons as we’ve never seen them before

A quantum simulator could open the door to advanced new materials, and better predict the weather, experts say
Researchers say new device allows them to observe electrons in a state of ‘quantum disorder’

Science

Ling Xinin Ohio

Published: 5:00pm, 18 Sep 2022

Why you can trust SCMP

An international team of scientists have created a device to peer into the melting of electrons – an area of research that they say could lead to the development of new materials and even computers that work like our brains.

Physicists from mainland China, Hong Kong, and Japan have developed a device that used specially structured carbon atoms to observe electrons. As the electrons changed from a crystal state to a liquid state, they discovered an intermediate phase that had never been seen before, according to their report in the journal Nature on Wednesday.

Scientists have long sought to tailor materials at the atomic level to achieve specific properties. But to do that, they first need to understand the complex interaction of electrons in a material – when for example, the electrons start to repel one another once that material is cold enough.

The problem has been almost impossible to solve with conventional computers. Cheng Bin from Nanjing University, the study’s co-lead, said the complexity of the interactions of electrons increases exponentially as the number of electrons increases, so calculating the properties of 100 interacting electrons, for example, would overwhelm today’s fastest computer. Now, however, researchers have a method to observe the properties of 10,000 electrons.

Chinese chip experts debate impact of US Chips Act but see no quick solutions

To tackle the dilemma, Cheng and his colleagues developed a quantum simulator by building an “atomic Lego set” with graphene, a single layer of carbon atoms arranged in a honeycomb lattice structure that produces excellent conductivity and strength.

The researchers first prepared two separate pieces of double-layered graphene, and positioned them at a specific angle to each other. They then cooled the arrangement to nearly absolute zero, and applied an electric field that was perpendicular to the graphene.

Like water molecules in an ice cube, the electrons in the material appeared to be frozen in their own positions. These electron crystals showed high resistance, completely altering the electronic property of the original graphene material.

When the researchers tuned down the electric field, they found it triggered a phenomenon called quantum fluctuation, causing tiny, random changes in the positions of the electrons. Gradually, more electrons started to move around until all of them were freed to flow like liquid water.

The team also observed an intermediate phase between the crystal and liquid states of the electrons. “It was neither solid nor liquid, but a quantum disorder,” Cheng said.

Iron Man-style hi-tech glasses could be developed for Hong Kong police

The quantum disordered state could be eliminated by adding a horizontal magnetic field to the material – just like melting ice directly to water, he added.

The most challenging part of the study was to precisely stack the graphene layers to an exact position and angle, Cheng said. “Graphene is as slippery as soap when stacked. It took us over a year to fix them to where they belong.”

But once that challenge was overcome, the researchers found their device was very easy to work with – simulating complex quantum processes simply by fine tuning electric or magnetic fields.

02:45

China’s ‘science grandma’: retired professor goes viral with quirky physics videos on social media

Researchers say the quantum simulator has great implications for future research and development.

For instance, it could be used to simulate complex systems found in the natural world to help develop superconducting materials and drugs that would have otherwise been impossible. It might even lead to techniques to simulate meteorological conditions to help predict weather, or biological neural networks to develop artificial intelligence that more closely mimics the human brain, Cheng said.