Summary
Researchers have made a groundbreaking advancement by successfully creating an ideal Weyl semimetal, a significant leap forward in the field of quantum materials. This discovery effectively resolves a decade-long challenge in isolating Weyl fermions within materials.
Weyl fermions are unique quantum excitations in crystals with special electromagnetic properties. Despite extensive research, unwanted electrons in most materials hide Weyl fermions. Recently, researchers created a material with only Weyl fermions and no unwanted electronic states.
An international team led by RIKEN‘s Strong Correlation Quantum Transport Laboratory created the first ideal Weyl semimetal, solving a decade-old problem in quantum materials. Over four years, researchers from various institutions collaborated to create a Weyl semimetal from a topological semiconductor, a strategy first proposed in 2011 but forgotten until now.
Semiconductors have a small energy gap, allowing them to switch between insulating and conducting states, which is key for transistors. Semimetals have no energy gap and are rare in real materials. Graphene is a well-known example.
In this study, researchers used the topological semiconductor bismuth telluride (Bi2Te3) and substituted chromium for bismuth to create (Cr, Bi)2Te3. They observed a large anomalous Hall effect (AHE) in this material, indicating new physics. The simple electronic structure of (Cr, Bi)2Te3 allowed researchers to link the large AHE to emergent Weyl fermions.
First author Ilya Belopolski of CEMS was surprised by the finding, noting that key insights were already established but not effectively communicated, delaying the discovery. Belopolski credits the breakthrough to the unique combination of talented researchers, generous funding, and the dynamic intellectual atmosphere at RIKEN. He highlights that the discovery happened at RIKEN due to its creative and collaborative environment.
Weyl semimetals can absorb low-frequency light, including terahertz (THz) frequencies, because they have no energy gap. Researchers are exploring their use in THz devices, high-performance sensors, low-power electronics, and novel optoelectronics. Postdoctoral researcher Lixuan Tai is excited about the new research opportunities for this material.
Journal Reference:
- Ilya Belopolski, Ryota Watanabe, Yuki Sato, Ryutaro Yoshimi, Minoru Kawamura, Soma Nagahama, Yilin Zhao, Sen Shao, Yuanjun Jin, Yoshihiro Kato, Yoshihiro Okamura, Xiao-Xiao Zhang, Yukako Fujishiro, Youtarou Takahashi, Max Hirschberger, Atsushi Tsukazaki, Kei S. Takahashi, Ching-Kai Chiu, Guoqing Chang, Masashi Kawasaki, Naoto Nagaosa, Yoshinori Tokura. Synthesis of a semimetallic Weyl ferromagnet with point Fermi surface. Nature, 2025; DOI: 10.1038/s41586-024-08330-y
Source: Tech Explorist
