A new Monash journal highlights recent research on heterostructures of topological insulators and magnetic materials.
In such heterostructures, the interesting interplay of magnetism and topology can give rise to new phenomena such as quantum anomalous Hall insulators, axis insulators and skyrmions. All of these are promising building blocks for the future of low-power electronics.
Provided that suitable candidate materials are found, it is possible to achieve these exotic states at room temperature and without any magnetic fields, thus helping the FLEET to search for future low energy electronics, beyond CMOS.
“Our aim was to investigate promising new methods to achieve the quantum Hall effect,” says lead author of the new study, Dr Semonti Bhattacharyya of Monash University.
Quantum Hall Effect (QHE) is a topological phenomenon that allows high-speed electrons to flow around the periphery of a material, which is potentially useful for future low-energy electronics and spintronics.
“However, a major bottleneck for this technology to be useful is the fact that the quantum Hall effect still requires high magnetic fields, which is not possible without high power consumption or cryogenic cooling. “
“There is no point in developing” low energy “electronics that consume Following energy to make them work! ”says Dr Bhattacharyya, researcher at FLEET, looking for a new generation of low-energy electronics.
However, a “cocktail” of topological physics and magnetism can achieve a similar effect, the quantum anomalous Hall effect, where similar edge states appear without applying an external magnetic field.
Several strategies have been followed to induce magnetism in topological insulators:
- by incorporating a magnetic impurity,
- using intrinsically magnetic topological insulators
- by inducing magnetism by proximity effect in topological insulator-magnetic insulator heterostructures.
“In our review, we focused on recent scientific research on the heterostructures of the third approach,” says co-author Dr Golrokh Akhgar (FLEET / Monash). That is, a unique structure incorporating thin layers of topological insulators and magnetic materials adjacent to each other, allowing the topological insulator to borrow magnetic properties from its neighbor.
This approach allows researchers to tune each type of material, for example by increasing the critical temperature for the magnetic material, and increasing the band gap and decreasing fault states, in topological materials.
“We believe this approach to induce magnetism in topological insulators holds the most promise for future breakthroughs, as magnetism and topology can be individually tuned in two different materials, thus optimizing both to our advantage,” says the co -author Matt Gebert (FLEET / Monash).
Another important feature of this heterostructure is that the induced magnetism depends only on the magnetic moments of the closest plane inside the magnetic material. This increases the number of candidate magnetic materials, allowing the choice of materials with magnetism at higher temperatures, for operation closer to room temperature.
“This is an exciting new area of research,” says the corresponding author, Professor Michael Fuhrer, also at Monash University.
“Progress is extremely rapid and we thought it was time to publish a review article summarizing recent achievements and outlining a future roadmap in this area,” said Professor Fuhrer, Director of FLEET.
This journal provides all the information necessary to introduce new researchers in the field. It explains the conceptual ideas behind the mechanisms of the magnetic proximity effect in topological insulators, presents the material systems that have been explored and the various emerging phenomena that have been detected, and plots a future roadmap towards increasing temperature and innovative applications.
“We hope others will find there a timely journal clarifying important concepts in the field and recent publications,” Semonti said.