Topological materials gather a lot of interest for their remarkable properties (very high
magnetoresistance, high carrier mobility…). Due to the strong intertwinement between
the electronic, structural, and topological degrees of freedom in these materials, a lightinduced
control of their structure would open the possibility to tune their properties and
topological phase. A first step towards this exciting possibility is to understand the carrier
and phonon dynamics in such systems.
The development of the Terahertz Time Domain Spectroscopy (THz-TDS) technique has
opened many possibilities to characterize modes in matter that were until then
inaccessible (intraband carrier dynamics, phonon modes, magnons…). By integrating this
time-resolved technique into a pump-probe configuration, one can investigate the
ultrafast transient photoconductive response and carrier dynamics of a broad range of
materials. I developed such set-up to conduct optical pump – THz probe measurements
on several samples.
I will first present a study of photo-induced carrier dynamics in a low bandgap
semiconductor Indium Antimonide (InSb) and I will discuss and model the influence of
pump fluence on these dynamics. In a second part, I will report similar pump-probe
measurements on the topological semi-metal zirconium pentatelluride (ZrTe5), that
allowed the study of its ultrafast carrier dynamics. I will complement these results with a
study of its structure’s dynamics conducted by time-resolved Raman spectroscopy.