Ultrafast carrier dynamics of SmB$_{6}$

SmB$_{6}$, a Kondo insulator, has generated lots of interest recently due to the proposed topological insulator state at low temperature. Ultrafast spectroscopy can produce valuable information on carriers/lattice dynamics and their interactions. Here we report femtosecond pump-probe experiment performed in SmB$_{6}$ single crystals and epitaxial thin films at variable temperatures. The observed carrier relaxations as well as different collective oscillation modes in GHz - THz range allow us to study the hybridization gap and the carrier coherence in different samples.