Enhanced ultrafast relaxation rate in the Weyl semimetal phase of MoTe2 measured by time- and angle-resolved photoelectron spectroscopy

This record contains the results of the first experimental investigation of the change in the electron dynamics across the topological phase transition from the type-II Weyl semimetal phase of MoTe2 to the trivial phase. By using the capability of time-resolved ARPES to access the unoccupied density of states, we succeed in transiently populating the Weyl points, which are otherwise above the Fermi level and out of the reach of conventional ARPES. We observe a bottleneck in the electron dynamics when the Weyl points annihilate and gaps are opened in the high-temperature trivial phase. This interpretation is supported by the observation that, in the "sister" compound WTe2 the dynamics is not affected by the change in temperature, and it is always much slower, thus reflecting the larger energy separation between the valence and conduction band.