Darius-A. Deaconu (University of Tokyo): From (lack of) Symmetry to Experiment: Exploring Weyl Semimetals in Real Materials

2F Seminar Room, Science Knot and Zoom

Abstract

Weyl semimetals are a fascinating class of quantum materials in which the electronic structure hosts Weyl points, which represent topologically protected band crossings that behave as magnetic monopoles in momentum space. Their unusual properties emerge from the interplay between symmetry, topology and the microscopic structure of real materials. Yet, finding material candidates that host well-isolated Weyl nodes and whose signatures are readily accessible experimentally remains a challenging problem.

In this talk, I will explore this issue from both theoretical and experimental perspectives. I will first introduce a low-symmetry model for Weyl semimetals and discuss how effects such as spin-orbit coupling and Fermi-surface warping shape their electronic structure. Using these ideas as design principles, I will then present a first-principles study identifying Cu2SnSe3 as a promising candidate for an ideal Weyl semimetal [1].

I will then turn to TaAs, where we combine theoretical calculations with quantum-oscillation experiments to probe the Fermi-surface pockets surrounding the Weyl points. By comparing the predicted and measured Shubnikov-de Haas oscillations, we obtain excellent agreement between theory and experiment, providing a direct connection between the underlying band topology and experimentally observable electronic properties [2].

Together, these studies illustrate two complementary aspects of the study of topological materials: using fundamental principles to design models and identify real material platforms, and connecting theoretical predictions to experimentally measurable signatures.

[1] D.-A. Deaconu, et al. “Low-Symmetry Weyl Semimetals: A Path to Ideal Topological States.” Advanced Functional Materials e06483 (2025).
[2] H. Murakawa, et al. “Observation of Zeeman splitting in the spin-polarized chiral fermion state in the Weyl semimetal TaAs.” Physical Review B 112, 045117 (2025).

Zoom information

https://us02web.zoom.us/j/2022111100

(Meeting code: 2022111100 Password: skcm2)

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