Resonant Raman scattering in crystalline GeSe2

The relationship between the local structures and the electronic stares of layered crystalline GeSe2 are studied by resonant Raman scattering. We observe 34 Raman-active modes of symmetry A(g), and find a selective resonant enhancement of the modes. Almost all the modes are enhanced around 2.7 eV except the two modes. This selective enhancement is attributed to the resonant effect with the localized exciton. We find the essential difference in the atomic motions between the resonant and nonresonant modes. Such behaviors are explained by a structural model of the localized exciton.