Abstract-Ultrafast terahertz response of multilayer graphene in the nonperturbative regime

P. Bowlan, E. Martinez-Moreno, K. Reimann, T. Elsaesser, and M. Woerner
http://prb.aps.org/accepted/ed078Y8aSf212448242681137542a700e758b25c0
The nonlinear dynamics of electrons in multi-layer epitaxial graphene is investigated by time-resolved terahertz (THz) spectroscopy in a regime where the interaction of electrons with the external field dominates over scattering processes. The predominantly coherent electron response to the THz field involves both intra- and interband currents, leading to coherently driven interband transitions of carriers and to the generation of higher harmonics of the THz carrier frequency. The overall behavior of the graphene layers is always absorptive, even after generation of an initial electron-hole distribution by femtosecond mid-infrared excitation. The results are in agreement with theoretical calculations of the nonperturbative THz response.