Non-equilibrium carrier dynamics in the unoccupied surface states of the magnetic Weyl semimetal candidate EuCd₂As₂

The nature of the material EuCd₂As₂, initially characterized as a magnetic (centrosymmetric) Weyl semimetal, has been under vigorous debate, with some recent studies demonstrating it to be a trivial magnetic semiconductor. Here, using time- and angle-resolved photoemission spectroscopy (tr-ARPES) with an infrared pump, we study the unoccupied band structure of ferromagnetically stabilized semi-metallic EuCd₂As₂, both in the vicinity of and far above the Fermi level. We further extract the decay dynamics of the nonequilibrium carrier distribution as a function of temperature and incident pump fluence, and observe an unusually long carrier lifetime that saturates at high photoexcited carrier density. We discuss our results in the context of possible carrier scattering mechanisms in the predicted Weyl semimetal phase in this material.