Resonant Raman scattering of few layers CrBr3

Łucja Kipczak; Arka Karmakar; Magdalena Grzeszczyk; Róża Janiszewska; Tomasz Woźniak; Zhaolong Chen; Jan Pawłowski; Kenji Watanabe; Takashi Taniguchi; Adam Babiński; Maciej Koperski; Maciej R. Molas

doi:10.1038/s41598-024-57622-w

Journal article Resonant Raman scattering of few layers CrBr3

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Łucja Kipczak, Arka Karmakar, Magdalena Grzeszczyk, Róża Janiszewska, Tomasz Woźniak, Zhaolong Chen, Jan Pawłowski, Kenji Watanabe, Takashi Taniguchi, Adam Babiński, Maciej Koperski, Maciej R. Molas. Resonant Raman scattering of few layers CrBr3. Scientific Reports. 2024, 14 (1), 7484. https://doi.org/10.1038/s41598-024-57622-w

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We investigate the vibrational and magnetic properties of thin layers of chromium tribromide (CrBr3) with a thickness ranging from three to twenty layers (3 L to 20 L) revealed by the Raman scattering (RS) technique. Systematic dependence of the RS process efficiency on the energy of the laser excitation is explored for four different excitation energies: 1.96 eV, 2.21 eV, 2.41 eV, and 3.06 eV. Our characterization demonstrates that for 12 L CrBr3, 3.06 eV excitation could be considered resonant with interband electronic transitions due to the enhanced intensity of the Raman-active scattering resonances and the qualitative change in the Raman spectra. Polarization- resolved RS measurements for 12 L CrBr3 and first-principles calculations allow us to identify five observable phonon modes characterized by distinct symmetries, classified as the Ag and Eg modes. The evolution of phonon modes with temperature for a 20 L CrBr3 encapsulated in hexagonal boron nitride flakes demonstrates alterations of phonon energies and/or linewidths of resonances indicative of a transition between the paramagnetic and ferromagnetic state at Curie temperature (TC ≈ 50 K). The exploration of the effects of thickness on the phonon energies demonstrated small variations pronounces exclusively for the thinnest layers in the vicinity of 3 - 5 L. This observation is attributed to strong localization in the real space of interband electronic excitations, limiting the effects of confinement for resonantly excited Raman modes to atomically thin layers.

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