Topological Insulating Phase Predicted in a New Type of Material
November 23, 2018 | RIKENEstimated reading time: 2 minutes
A class of materials called electrides could harbor exotic topological properties, according to calculations by RIKEN scientists. This prediction promises to broaden the types of materials whose topological properties can be exploited in new devices.
Topology is an area of mathematics that describes an object in terms of those physical properties that remain the same even when the shape of the object changes. It has been an important theoretical concept in quantum and particle physics for decades, but the last few years has seen the emergence of materials that exhibit extraordinary properties due to topology.
Many types of topological materials have been identified, including topological insulators and topological semimetals. In topological insulators, electrons can scud across the material’s surface but cannot travel below the surface. That is because the surface electrons exist in a quantum mechanical state that is geometrically ‘twisted’.
This special topology protects surface states, imparting them with remarkable resilience to impurities and imperfections in the material. This robustness makes topological matter an exciting prospect for a new generation of information processing devices.
To date, the search for new topological materials has largely been limited to matter that includes heavy elements with intrinsic magnetic properties, such as bismuth. This greatly narrows the choice of potentially useful materials. Now, Motoaki Hirayama from the RIKEN Center for Emergent Matter Science and his colleagues have shown that an entirely different class of materials, known as electrides, can also exhibit topological properties.
Like common table salt (sodium chloride), electrides are ionic crystals—ordered arrays of positively charged cations and negatively charged anions. But in electrides, the anions are electrons rather than ions. Some of the electrons prefer to sit between the atomic nuclei in the crystal structure. This means they are less influenced by the nuclei’s electric fields and so are weakly bound to the atomic lattice. Hirayama and co-workers theoretically modeled the behavior of these electrons various electride materials using so-called first-principles calculations.
“For example, we found an exotic topological state in the electride scandium carbide,” says Hirayama. “Thanks to its nontrivial topology and electride properties, its topological charges float on the material’s surface.”
The team found that electrides can support various topological phases, including both topological insulating and topological semimetal phases. And they suggest that these effects could be observed using commonly used experimental techniques, such as scanning tunneling microscopy and angle-resolved photoelectron spectroscopy.
“The next step is to further investigate the physical properties of these topological electrides,” says Hirayama. “We expect them to be a rich source of physics.”
Suggested Items
SMC Korea 2024 to Highlight Semiconductor Materials Trends and Innovations on Industry’s Path to $1 Trillion
04/24/2024 | SEMIWith Korea a major consumer of semiconductor materials and advanced materials a key driver of innovation on the industry’s path to $1 trillion, industry leaders and experts will gather at SMC (Strategic Materials Conference) Korea 2024 on May 29 at the Suwon Convention Center in Gyeonggi-do, South Korea to provide insights into the latest materials developments and trends. Registration is open.
Groundbreaking Ceremony Marks the Beginning of a New Era for Newccess Industrial; The Construction of the MINGXIN Building
04/12/2024 | Newccess IndustrialOn a clear and sunny day in March, the groundbreaking ceremony for the MINGXIN Building took place in Shenzhen, China. This moment marked the official commencement of construction for a project that will reshape the semiconductor materials industry.
The Need for a Holistic Global Sustainability Standard
04/10/2024 | Michael Ford, Aegis SoftwareNo one can deny that the resources of our fragile planet are finite. The environment seems like a third party, subject to constant degradation. We’re acutely aware of the effects of pollution on our climate, and despite our “throw-away” culture, recycling and recovery of materials has remained relatively expensive, even as we use more energy just to survive.
iNEMI Publishes Four Roadmap Topics
04/04/2024 | iNEMIThe International Electronics Manufacturing Initiative (iNEMI) announces the availability of the first roadmap topics in the new iNEMI Roadmap format. Printed circuit boards, sustainable electronics, smart manufacturing, and mmWave materials and test are now available online.
Insulectro’s 'Storekeepers' Extend Their Welcome to Technology Village at IPC APEX EXPO
04/03/2024 | InsulectroInsulectro, the largest distributor of materials for use in the manufacture of PCBs and printed electronics, welcomes attendees to its TECHNOLOGY VILLAGE during this year’s IPC APEX EXPO at the Anaheim Convention Center, April 9-11, 2024.