Annawati, Bergitta DwiBergitta DwiAnnawatiArun Kumar, Kalingarayanpalayam MatheswaranKalingarayanpalayam MatheswaranArun KumarTUAN HUNG NGUYENChang, YuchenYuchenChangChen, ShihchiehShihchiehChenLu, T. H.T. H.LuHuang, XianglinXianglinHuangLan, YinpingYinpingLanShu, GuojiunGuojiunShuSaito, RiichiroRiichiroSaito2025-09-242025-09-242025https://www.scopus.com/inward/record.uri?eid=2-s2.0-105009935576&doi=10.1002%2Fjrs.70004&partnerID=40&md5=19fdc8cb9d1eb93b8d97c232d2578dc7https://scholars.lib.ntu.edu.tw/handle/123456789/732345We present the polarized Raman spectra of 2H-NbSe (Formula presented.) and 1T-VSe (Formula presented.) single crystals. The phonon symmetries of the first-order Raman-active modes in both materials are identified using linearly and circularly polarized Raman spectroscopy. In particular, the Raman peak of 1T-VSe (Formula presented.) at 250 cm (Formula presented.), previously assigned to the E (Formula presented.) mode, is reinterpreted as two-phonon combinational modes at the M point in the Brillouin zone. The helicity-dependent Raman spectroscopy enables the separation of the overlapping A (Formula presented.) and E (Formula presented.) modes in 2H-NbSe (Formula presented.). The second-order phonon modes exhibit either helicity-conserving or helicity-changing behavior. The first-principles calculations of phonon dispersion and the two-phonon density of states support the assignment of the two-phonon modes. The calculated shear and layer breathing modes of 2H-NbSe (Formula presented.) appear at 37 and 53 cm (Formula presented.), respectively, while the calculated E (Formula presented.) mode of 1T-VSe (Formula presented.) appears at 139 cm (Formula presented.).review article10.1002/jrs.700042-s2.0-105009935576