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タイトル：Raman scattering spectroscopy as a probe of the magnetic Weyl semimetal state.
講演者：Natalia Drichko 氏
　　　　Johns Hopkins University　教授
日時：2025年10月3日（金）15:00～16:30  (JST)　
場所：東京大学理学部1号館　913号室　

In magnetic Weyl semimetals, the intrinsic anomalous Hall effect arises from non-zero Berry curvature near the Weyl nodes. However, to clearly establish Weyl semimetal evidence of the topological electronic structure and a particular form of time reversal symmetry breaking order is needed.

In this presentation, I demonstrate how Raman scattering spectroscopy can be used to probe low-frequency electronic structure and magnetism in Weyl semimetals using examples of Nd2Ir2O7 and V1/3NbS2. Frequency dependence of electronic Raman scattering within Weyl nodes is proportional to the density of states and depends on dimensionality, thus revealing the linear q-dependence of the density of states down to low frequencies unaccessible for the most part with other optical techniques. Simultaneously probing magnetic Raman scattering identifies a magnetic phase transition. In this way, polarization-dependent electronic and magnetic Raman scattering demonstrates the presence of the band structure and form of time reversal symmetry breaking necessary to realize a Weyl semimetal state.  I will also show how scattering of optical phonons on the electrons in a semimetal can be a tool to probe the electronic bands.