Fig. 1
a Raman spectroscopy on a V2O3 single crystal with the c axis perpendicular to the surface at 295 K. The A1g phonon mode is visible at 7.4 THz in the parallel polarization configuration (VV). The vertical dashed line indicates the phonon frequency as derived by fitting the time resolved reflectivity curve in b. b pump-probe reflectivity at a 8 mJ/cm2 fluence on the same specimen in the same experimental conditions, at 295 K. At the top, the background subtracted experimental data are compared with the best sinusoidal fit with a 7.7 THz frequency (in red). At the bottom, the same data are compared to the same sinusoidal function but at 7.4 THz (in blue), corresponding to the Raman frequency. c comparison between thermal and pump-probe shifts. At 200 K, the A1g mode frequency is 7.58 THz; by increasing the temperature to 300 K (ΔT = 100 K) the Raman frequency presents a red shift of 0.16 THz; conversely, under ultrafast excitation, it undergoes a blue-shift of 0.35 THz. d low fluence measurements performed at 20 μJ/cm2 at room temperature; these data were obtained at a repetition rate of 5 MHz. The best fit (green curve) gives a frequency of 7.56 THz
