Observation of fast Auger scattering in Landau-quantized graphene
Graphene subject to the external magnetic field, with its electronic states quantized into a discrete Landau levels, represents a natural playground to study interactions among charged Dirac-type carriers. Fractional quantum Hall effect, nowadays widely explored in both graphene monolayer and bilayer, is the most representative demonstration of such correlated-electron phenomena.
A recent publication, resulting from an international collaboration of researchers from Germany, France, and USA, reports on another manifestation of electron-electron interaction in Landau-quantized graphene, this time observed in a purely optical experiment. Exciting electrons between Landau levels by pulsed infrared laser, time-resolved spectroscopy (pump-probe technique) allowed the researchers to study mechanisms of carrier relaxation back to thermal equilibrium. Among them, surprisingly fast Auger processes (electron-electron scattering) have been identified. Such processes are well-known and studied in conventional materials, nevertheless, they were originally expected to vanish in graphene due to its specific non-equidistant spacing of Landau levels. Understanding such efficient Auger scattering in graphene represents a basic prerequisite for possible construction of Landau level laser on Dirac-type electrons – theoretically predicted widely tunable source of infrared radiation.
Fig. 1 : Relative changes of graphene’s transmission induced by a picosend pulse of infrared radiation for various magnetic fields. In the inset, the pump–probe experiment is schematically depicted.
M. Mittendorff, F. Wendler, E. Malic, A. Knorr, M. Orlita, M. Potemski, C. Berger, W. A. de Heer, H. Schneider, M. Helm and S. Winnerl, Nature Physics, aop (2014), doi :10.1038/nphys3164
Stephan Winnerl & Martin Mittendorff, HZ Dresden-Rossendorf (firstname.lastname@example.org)