We report Raman scattering measurements on URu2Si2 single crystals as a function of temperature down to 2 K. We probe all the Raman active symmetries. Only when the sample is prepared with a surface perpendicular to a-axis, we observe an extrinsic hardening and broadening of the A1g and B1g phonons after polishing, which disappears after annealing. Moreover, a parasitic phase with Si-excess compared to URu2Si2 composition appears on the a-axis surface when annealing is at 1075 °C. No parasitic phase is induced when annealing is done at 950 °C. The temperature dependance of the A1g, and two E g phonons shows a hardening with decreasing temperature. The B1g phonon mode's behavior is more unusual, its energy stays stable down to ∼ 30 K before softens at lower temperature. An electron-phonon coupling is certainly at play here.
- Raman spectroscopy
- Strongly correlated electron system