A “true” Weyl semimetal in (Cr,Bi)₂Te₃

Frontiers in magnetism & topology in quantum materials

报告人

Asst. Prof. Ilya Belopolski 

Nanyang Technological University, 

Singapore

时间

2025年12月11日（星期四）下午3：00

地点

物质科学教研楼B902会议室

报告摘要

Weyl semimetals are crystals where electronic quasiparticles take the form of Weyl fermions [1]. Such emergent Weyl fermions are massless, chiral and topological—potentially useful for circuit interconnects, ultrafast THz detectors and topological transistors. Despite these promising applications and a decade of intense worldwide research, our best Weyl semimetals to date are in fact basically metallic and dominated by irrelevant, conventional electrons [2-6]. To solve this problem, we took a different approach—we started from the topological semiconductor Bi₂Te₃ and used Cr doping to introduce ferromagnetism and drive a topological phase transition to a semimetal [7,8]. We observed that (Cr,Bi)₂Te₃ exhibits a record bulk anomalous Hall angle > 0.5 (the key figure of merit for a magnetic Weyl semimetal) along with non-metallic conductivity, sharply distinct from known Weyl materials and conventional ferromagnets. Together with theory, our experiments suggest that (Cr,Bi)₂Te₃ has a simple, semimetallic electronic structure composed of only two Weyl points, without irrelevant electronic states. Improving the crystalline quality should further increase the figure of merit, and could enable a richer exploration of Weyl light-matter interaction and non-linear response. Our design principle could further be broadened to analogous inversion-symmetry-breaking Weyl semimetals, robust up to room temperature, and multiferroic Weyl semimetals. The interplay of momentum-space Weyl topology with real-space magnetic structures such as skyrmions [9] and p-wave helices [10] offers a further rich playground for novel quantum phases of matter.

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[9] Max. T. Birch, I.B. et al. Nature 633, 554 (2024)

[10] R. Yamada, Max T. Birch… I.B… M. Hirschberger. Nature 646, 837 (2025)