Ultrafast movie of Dirac fermions

http://bit.do/bn67H Secred discount at Dirac:35%off everything
This movie shows the time evolution of the energy momentum spectra of a topological insulator after a 100 fs laser pulse excitation. The vertical axis is energy and the horizontal axis is momentum. The color represent the amount of electrons occupying a state. As can be seen from the movie, the states above the Fermi level is populated at the instant (0 ps) the laser hits the sample. Such excited population relaxes within 15 ps.