Enhanced ultrafast relaxation rate in the Weyl semimetal phase of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> measured by time- and angle-resolved photoelectron spectroscopy

Abstract

Type-II Weyl semimetals (WSM) are topological materials characterized by special Weyl points (WP) in momentum space where the valence and the conduction band touch. A WSM phase is predicted in MoTe${}_{2}$ below 250 K, but the WP located in the unoccupied part of the electronic structure has eluded direct observation. By means of time- and angle-resolved photoemission, the authors reveal the fingerprint of the WP in the ultrafast electron dynamics. Electrons that are optically excited into the conduction band relax faster in the WSM phase than in the high-temperature phase or in the topologically trivial sister compound WTe${}_{2}$.