Physicists Create Quantum Electronic Material Known As 'Kagome Metal'

Researchers from the Massachusetts Institute of Technology (MIT), Harvard University and the Lawrence Berkeley National Laboratory have announced that they have created an exotic new material as “kagome metal”.

This is an electrically conductive crystal consisting of layers of iron and tin atoms arranged in a kagome lattice pattern. Kagome is derived from traditional Japanese basket-making techniques. The kagome pattern consists of interlaced, symmetrical triangles arranged in a lattice.

Physicists have been fascinated by this pattern for decades and they have hypothesized that if the atoms of a metal or another conductive substance could be arranged in such a pattern, the resulting material could display exotic electronic properties. When an electric current was passed across the atomic layers in the crystal, the current was found to behave in very unusual ways.

The electrons in the current did not flow straight through the lattice as expected but they bent into tight circular paths and flowed along the edges without losing energy.

Displayed Quantum Hall Effect

The behavior of these electrons was found to be similar to something known as the quantum Hall effect in physics. This is a phenomenon seen in two-dimensional materials that come under a branch of physics known as quantum mechanics.

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Quantum mechanics is a fundamental theory in physics describing nature at the very smallest scales of atoms and subatomic particles. At such scales, objects can display some very different properties, such as having the characteristics of a wave and a particle at the same time.

“By constructing the kagome network of iron, which is inherently magnetic, this exotic behavior persists to room temperature and higher,” Joseph Checkelsky, assistant professor of Physics at MIT said. “The charges in the crystal feel not only the magnetic fields from these atoms, but also a purely quantum-mechanical magnetic force from the lattice. This could lead to perfect conduction, akin to superconductivity, in future generations of materials.”

Stabilizing at room temperature

To be able to make the metal, the team first brought iron and tin together and ground them. They then heated the resulting powder at 750 degrees Celsius.

This was the temperature, where the iron and tin atoms crystallized and arranged themselves in a kagome-patterned lattice. The crystals were then submerged in an ice bath and this made the lattice stable at room temperature. “The kagome pattern has big empty spaces that might be easy to weave by hand but are often unstable in crystalline solids, which prefer the best packing of atoms,” Linda Ye, co-author of the study and also from MIT, said.

“The trick here was to fill these voids with a second type of atom in a structure that was at least stable at high temperatures. Realizing these quantum materials doesn’t need alchemy, but instead materials science and patience.”

The researchers believe metals which are similar and have kagome lattices could prove useful in a wide range of applications from quantum computing to power lines which would not lose energy.