A global team has discovered two different topological states in the single-atom thick crystal TaIrTe4, which transition between insulation and conduction. The material has zero electrical conductivity inside, but its boundaries are conductive. The team’s research found that these two states have different origins and could be used to explore exotic quantum phases and electromagnetism.
A group of scientists led by Boston College physicists recently reported in the online version of the journal Nature about the discovery of unique electronic properties in a quantum material. They found a dual topological insulator that provides a new way to create topological flat minibands through electron interactions. This discovery offers a promising platform for exploring exotic quantum phases and electromagnetism, according to the team. Boston College Assistant Professor of Physics Qiong M and the team were able to produce high-quality, atomically-thin samples of TaIrTe4 and developed corresponding electronic devices for their experiments.The report’s lead author expressed his excitement about the discovery of not one, but two topological insulating states, which goes beyond theoretical predictions. The team has identified a new effect called the dual topological insulator or the dual quantum spin Hall insulator. The study focuses on extremely thin, two-dimensional layers of a crystalline material known as TaIrTe4, made from tantalum, iridium, and tellurium. The team of scientists involved in the study comes from various institutions including BC, MIT, Harvard University, UCLA, Texas A&M, the University of Tennessee, Nanyang Technological University in Singapore, and the Chinese Academy of S.The research was conducted by a team of scientists from the University of Tennessee, the Oak Ridge National Laboratory, Pennsylvania State University, the Chinese Academy of Sciences, and Japan’s National Institute for Materials Science. The team worked with layers of material that are less than 1 nanometer thick, making them more than 100,000 times thinner than a human hair. These thin layers, also known as “flakes,” were separated from a larger crystal using a basic method involving clear adhesive tape, which is a technique that has been honored with a Nobel Prize and is widely used in materials science.
The purpose of the investigation was to understand how these materials conduct electricity. Due to the extremely small size of the materials, advanced nanofabrication techniques such as photolithography and electron beam lithography were used to create nano-sized electronic structures…. materials to be highly tunable and able to transition between both magnetic and nonmagnetic states. This discovery opens up new opportunities for designing and developing future electronics using these materials. The researchers believe that the unique properties of TaIrTe4 can play a crucial role in advancing the field of energy-efficient electronic devices.Ma said that the material transitions between two different topological states. In both cases, the material has no electrical conductivity inside, but its boundaries are still conductive. The scientists have found that these two states have different origins through systematic experimental and theoretical investigation.
The scientists were surprised by the findings, which went beyond what was theoretically predicted.
Ma explained that typically, adding electrons to a material increases its conductivity because there are more charge carriers. At first, their system followed this expected behavior and became more conductive.There was a surprising discovery when adding electrons to a material — it initially becomes conductive, but then unexpectedly becomes insulating again once a certain point is reached. This insulating phase only allows electrical conduction at the boundaries without any energy loss, similar to the initial phase when the material had no electrons. This transition to a second insulating phase was completely unexpected. Future research on this discovery will involve collaborating with experts in nanoscale imaging probes and other specialized techniques to further understand this unexpected behavior.”Improving the quality of our material will enhance the already impressive dissipationless topological conduction,” stated Ma. “Additionally, we intend to construct heterostructures using this new material to unveil even more fascinating physical behaviors.”
At Boston College, Ma worked with Physics Professors Kenneth Burch and Ziqiang Wang, the University Clean Room staff, BC post-docs Jian Tang, Zumeng Huang, and Zhe Sun, as well as graduate students Thomas Siyuan Ding, Michael Geiwitz, Mohamed Shehabeldin, Vsevolod Belosevich, and Yiping Wang, along with Zihan Wang, a visiting undergraduate researcher.
Journal Reference
Researchers including Jian Tang, Thomas Siyuan Ding, and Hongyu Chen have discovered a dual quantum spin Hall insulator by density-tuned correlations in TaIrTe4. This groundbreaking finding was published in Nature in 2024 and can be accessed through the following DOI link: http://dx.doi.org/10.1038/s41586-024-07211-8.
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