Electrons zoom along quantum highways in a new material

Scientists have shown how MnBi₆The_ten, shown here in purple (tellurium), blue (bismuth), and green (manganese), can act as a magnetic topological insulator, conducting electric current (blue) along a “quantum highway” without loss of energy. The study revealed that a concerted action of different material defects is the key to quantum electronic properties. Credit: University of Chicago

Researchers from the Pritzker School of Molecular Engineering (PME) at the University of Chicago have discovered a new material, MnBi₆The_ten, which can be used to create quantum highways along which electrons can travel. These electron arteries are potentially useful for connecting the internal components of powerful and energy-efficient quantum computers.

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

In the new work, published in the journal Nano-lettersthe researchers detailed how MnBi₆The_ten acts as a “magnetic topological insulator”, passing electrons around its perimeter while retaining the energy and quantum properties of the electrons.

“We have discovered a material that has the potential to open up the quantum highway for electrons to flow without dissipation,” Asst said. Teacher. Shuolong Yang, who led the research. “This is an important step towards the engineering of topological quantum computers.”

Quantum connections

Quantum computers store data in qubits, a basic unit of information that exhibits quantum properties, including superposition. At the same time, researchers are working to develop devices that connect these qubits – sometimes in the form of single electrons – they also need new materials that can transmit the information stored in these qubits.

Theoretical physicists have proposed that electrons can be passed between topological qubits by forcing the electrons to flow through a one-dimensional conduction channel at the edge of a material. Previous attempts to do this required extremely low temperatures, which were not possible for most applications.

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

Yang’s group began to study MnBi₆The_ten, using manganese to introduce magnetization into the semiconductor formed from bismuth and tellurium. While electrons flow randomly inside most semiconductors, the magnetic field in MnBi₆The_ten forces all electrons in a single file line outside the material.

SME researchers obtained MnBi₆The_ten which had been made by collaborators of the 2D Crystal Consortium at Pennsylvania State University, led by Zhiqiang Mao. Next, the team used a combination of two approaches – angle-resolved photoemission spectroscopy and transmission electron microscopy (TEM) – to study exactly how electrons in MnBi₆The_ten behaved and how the motion of electrons varied with magnetic states. The TEM experiments were performed in collaboration with Nasim Alem’s Pennsylvania State University laboratory.

Faults sought

When they probed the properties of MnBi₆The_tenOne thing initially puzzled the research team: some pieces of the material seemed to work well as magnetic topological insulators, while others did not.

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

Through their TEM experiments, however, they revealed that all pieces of MnBi₆The_ten that worked had one thing in common: flaws in the form of lack of manganese scattered throughout the material. Further experiments showed that indeed these defects were necessary to conduct the magnetic state and allow electrons to flow.

“A very high value of this work is that, for the first time, we understood how to tune these defects to activate quantum properties,” Yang said.

Researchers are now investigating new methods of growing MnBi₆The_ten crystals in the lab, as well as probing what’s going on with ultra-thin, two-dimensional versions of the material.