Researchers have discovered that MnBi6Te10 (shown in purple (tellurium), blue (bismuth) and green (manganese)) can act as a magnetic topological insulator, conducting electrical current (blue) along a ‘quantum highway’ without losing energy. Image: University of Chicago Yang Lab.
Researchers have discovered that MnBi6Te10 (shown in purple (tellurium), blue (bismuth) and green (manganese)) can act as a magnetic topological insulator, conducting electrical current (blue) along a ‘quantum highway’ without losing energy. Image: University of Chicago Yang Lab.

Researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have discovered a new material, MnBi6Te10, that can be used to create quantum highways for electrons. These electron thoroughfares could be useful for connecting the internal components of powerful, energy-efficient quantum computers.

When electrons move through traditional metal wires, they lose a small amount of energy – as heat – and some of their intrinsic properties change. This means such wires cannot be used to connect components in quantum computers that encode data in the quantum properties of electrons.

In a paper in Nano Letters, the researchers report their discovery that MnBi6Te10 can act as a ‘magnetic topological insulator’, shuttling electrons around its perimeter while maintaining the electrons’ energy and quantum properties.

“We’ve discovered a material that has the potential to open the quantum highway for electrons to flow with no dissipation,” said Shuolong Yang, an assistant professor in PME, who led the research. “This is an important milestone toward the engineering of topological quantum computers.”

Quantum computers store data in qubits, a basic unit of information that exhibits quantum properties including superposition. Scientists are now working to develop devices that can connect such qubits – sometimes using single electrons – and new materials that can transmit the information stored in these qubits.

Theoretical physicists have proposed that electrons could be transmitted between topological qubits by forcing the electrons to flow in a one-dimensional conduction channel on the edge of a material. Previous attempts to do this have utilized extremely low temperatures that are not feasible for most applications.

“The reason we decided to look into this particular material is that we thought it would work at a much more realistic temperature,” said Yang.

Yang’s group began studying MnBi6Te10, where manganese adds magnetization to the semiconductor formed by bismuth and tellurium. While electrons flow randomly throughout the interior of most semiconductors, the magnetic field in MnBi6Te10 forces all electrons into a single-file line on the outside of the material.

The PME researchers obtained MnBi6Te10 that had been fabricated by collaborators at the 2D Crystal Consortium in Pennsylvania State University, led by Zhiqiang Mao. Then they used a combination of two approaches – angle-resolved photoemission spectroscopy and transmission electron microscopy (TEM) – to study exactly how the electrons within MnBi6Te10 behaved and how their movement varied with magnetic states. The TEM experiments were performed in collaboration with the Pennsylvania State University lab of Nasim Alem.

When they were probing the properties of MnBi6Te10, one thing stumped the research team at first: some pieces of the material seemed to work well as magnetic topological insulators, while other pieces didn’t.

“Some of them had the desired electronic properties and others didn’t, and the interesting thing was that it was very hard to tell the difference in their structures,” said Yang. “We saw the same thing when we did structural measurements such as X-ray diffraction, so it was a bit of a mystery.”

Through their TEM experiments, however, they discovered that all the pieces of MnBi6Te10 that worked had something in common: they all had defects in the form of missing manganese scattered throughout the material. Further experiments showed that these defects were required to drive the magnetic state and allow electrons to flow.

“A very high value of this work is, for the first time, we’ve figured out how to tune these defects to enable quantum properties,” said Yang.

The researchers are now pursuing new methods for growing MnBi6Te10 crystals in the lab, as well as probing what happens with ultra-thin, two-dimensional versions of the material.

This story is adapted from material from the University of Chicago, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.