【时间】2026年7月15日（星期三）14:00

【地点】量子院526报告厅

【主持】 Panagiotis Kotetes 副研究员 凝聚态理论团队

【题目】Emergent Topology, Chirality, and Quantum Geometry in Phonon spectra

【摘要】The wavefunction of phonons encodes rich quantum information, including topological and chiral properties. In phonon systems, “chirality” carries distinct meanings: topological chirality defined in k-space and rotational chirality associated with nonzero angular momentum. In this talk, I will first introduce both types of chirality and highlight key experimental observations, such as in FeSi [1] (the first material identified with topological phonons), circularly polarized phonons in nonsymmorphic crystals like α-HgS and Te [2-3], and molecular Berry curvature–induced circularly polarized phonons in Co₃Sn₂S₂ [4-5]. I will then present our recent work: a general ab initio framework, which captures electronic order-driven symmetry breaking in lattice dynamics and applies to both insulating and metallic magnets. Applying this framework to Co₃Sn₂S₂ reveals distinct microscopic origins for the E₉ and E_u phonon modes [6]. Finally, I will discuss how to directly probe the quantum geometric tensor for phonons, including its imaginary part Berry curvature and real part quantum metric components, an approach extendable to other bosonic collective excitations [7]. 

References:

[1] Zhang, et al., Phys. Rev. Lett., 120, 016401 (2018).

[2] Ishito, … Zhang, … , Nat. Phys., 19, 35 (2023).

[3] Zhang, et al., Nano Lett., 23, 7561 (2023).

[4] Yang, … Zhang*..., Phys. Rev. Lett., 134, 196905 (2025).

[5] Che, … Zhang*..., Phys. Rev. Lett., 134, 196906 (2025).

[6] Zhang, … Zhang*, Sci. Adv., 12, eaed7081 (2026).

[7] Wu, Oka, Murakami,  Zhang*, arXiv:2601.13963 (2026).

【报告人简介】Dr. Zhang received her B.S. degree from Beijing Normal University in 2014 and her Ph.D. in Physics from the Institute of Physics, Chinese Academy of Sciences, in 2019. From 2019 to 2022, she conducted postdoctoral research and subsequently served as a Specially Appointed Assistant Professor at the Tokyo Institute of Technology, Japan. She joined the Institute of Theoretical Physics, Chinese Academy of Sciences, in 2023, where she is currently an Associate Professor.

Her research focuses on computational condensed matter physics, with particular interests in the theory of topological quantum materials and the discovery of novel topological phases and their emergent properties, including those associated with electrons, phonons, and electron–phonon interactions. She successfully predicted several topological phonon materials, including the Weyl phonon materials FeSi, and the nodal-line phonon material MoB?. She also established Materiae, the world's first topological materials database, whose related achievements were selected as one of the Top Ten Scientific and Technological Advances in China in 2019 by members of the Chinese Academies.

To date, Dr. Zhang has published more than 50 SCI-indexed papers, which have received over 4,800 citations. Her honors include the Young Outstanding Scholar Award (Most Promising Award) from the Alibaba DAMO Academy (2023), the Asia Pacific Condensed Matter Physics Young Scientist Award (2024), and selection as one of the MIT Technology Review Innovators Under 35 (Asia Pacific) in 2025.