Browsing by Author "Rojas, Laura (TTU)"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Observation of the polaronic character of excitons in a two-dimensional semiconducting magnet CrI3(2020) Jin, Wencan; Kim, Hyun Ho; Ye, Zhipeng (TTU); Ye, Gaihua (TTU); Rojas, Laura (TTU); Luo, Xiangpeng; Yang, Bowen; Yin, Fangzhou; Horng, Jason Shih An; Tian, Shangjie; Fu, Yang; Xu, Gongjun; Deng, Hui; Lei, Hechang; Tsen, Adam W.; Sun, Kai; He, Rui (TTU); Zhao, LiuyanExciton dynamics can be strongly affected by lattice vibrations through electron-phonon coupling. This is rarely explored in two-dimensional magnetic semiconductors. Focusing on bilayer CrI3, we first show the presence of strong electron-phonon coupling through temperature-dependent photoluminescence and absorption spectroscopy. We then report the observation of periodic broad modes up to the 8th order in Raman spectra, attributed to the polaronic character of excitons. We establish that this polaronic character is dominated by the coupling between the charge-transfer exciton at 1.96 eV and a longitudinal optical phonon at 120.6 cm−1. We further show that the emergence of long-range magnetic order enhances the electron-phonon coupling strength by ~50% and that the transition from layered antiferromagnetic to ferromagnetic order tunes the spectral intensity of the periodic broad modes, suggesting a strong coupling among the lattice, charge and spin in two-dimensional CrI3. Our study opens opportunities for tailoring light-matter interactions in two-dimensional magnetic semiconductors.Item Tunable layered-magnetism-assisted magneto-Raman effect in a two-dimensional magnet CrI3(2020) Jin, Wencan; Ye, Zhipeng (TTU); Luo, Xiangpeng; Yang, Bowen; Ye, Gaihua (TTU); Yin, Fangzhou; Ho Kim, Hyun; Rojas, Laura (TTU); Tian, Shangjie; Fu, Yang; Yan, Shaohua; Lei, Hechang; Sun, Kai; Tsen, Adam W.; He, Rui (TTU); Zhao, LiuyanWe used a combination of polarized Raman spectroscopy experiment and model magnetism-phonon coupling calculations to study the rich magneto-Raman effect in the two-dimensional (2D) magnet CrI3. We reveal a layered-magnetism-assisted phonon scattering mechanism below the magnetic onset temperature, whose Raman excitation breaks time-reversal symmetry, has an antisymmetric Raman tensor, and follows the magnetic phase transitions across critical magnetic fields, on top of the presence of the conventional phonon scattering with symmetric Raman tensors in N-layer CrI3. We resolve in data and by calculations that the first-order Ag phonon of the monolayer splits into an N-fold multiplet in N-layer CrI3 due to the interlayer coupling (N≥2) and that the phonons within the multiplet show distinct magnetic field dependence because of their different layered-magnetism-phonon coupling. We further find that such a layered-magnetism-phonon coupled Raman scattering mechanism extends beyond first-order to higher-order multiphonon scattering processes. Our results on the magneto-Raman effect of the first-order phonons in the multiplet and the higherorder multiphonons in N-layer CrI3 demonstrate the rich and strong behavior of emergent magneto-optical effects in 2D magnets and underline the unique opportunities of spin-phonon physics in van der Waals layered magnets.