Effects of electron-electron interactions on the electronic Raman scattering of graphite in high magnetic fields

We report the observation of strongly temperature (T)-dependent spectral lines in electronic Raman-scattering spectra of graphite in a high magnetic field up to 45 T applied along the c axis. The magnetic field quantizes the in-plane motion, while the out-of-plane motion remains free, effectively reducing the system dimension from 3 to 1. Optically created electron-hole pairs interact with, or shake up, the one-dimensional Fermi sea in the lowest Landau subbands. Based on the Tomonaga-Luttinger liquid theory, we show that interaction effects modify the spectral line shape from (omega - Delta)(-1/2) to (omega - Delta)(2 alpha-1/2) at T = 0. At finite T, we predict a thermal broadening factor that increases linearly with T. Our model reproduces the observed T -dependent line shape, determining the electron-electron interaction parameter alpha to be similar to 0.05 at 40 T.