Time- and angle-resolved photoemission studies of ZrTe5

With a surge of interest in various topological states of matter, ZrTe$_{\mathrm{5}}$ has been recently reinvestigated due to its unique electronic and optical properties. While there is still an ongoing debate about whether ZrTe$_{\mathrm{5}}$ is a strong/weak topological insulator or a Dirac semimetal, time-resolved studies and information about the conduction band have been lacking. Here, we report time- and angle-resolved photoemission measurements performed on single crystals of ZrTe$_{\mathrm{5\thinspace }}$with various pump laser pulses with energies ranging from near- to mid-infrared. Our results reveal relaxation dynamics across different energies and set a limit on the topological classification of ZrTe$_{\mathrm{5}}$.