Electric toroidal octupolar symmetry in pyrite FeS2 probed by Raman optical activity
Abstract
We report Raman optical activity in pyrite FeS2, which hosts an electric toroidal octupolar symmetry. A clear and reproducible sign reversal of the circular intensity difference is observed between neighboring \111\ faces under cross-circular polarization. The signal appears only for the doubly degenerate Eg phonon mode and is absent for other modes, consistent with symmetry analysis. First-principles calculations reproduce these features, establishing Raman optical activity as a probe of higher-rank axial multipolar symmetry.
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