Orbital selective dynamics in Fe-based systems using time-resolved ARPES

Abstract

Exoticity in material properties is often linked to the complex interplay of spin, charge, orbital and lattice degrees of freedom that makes the study of the origin of such exoticity difficult. The outstanding issue is to disentangle parameter space and reveal the underlying physics. We propose a unique method to excite electrons of a selected symmetry without significant effect on other electrons using polarized pump light pulse in a pump-probe experiment. Using this technique, we show that the relaxation of itinerant electrons occurs faster than the local electrons; the first experimental identification of the orbital selective electron dynamics in a complex correlated system, EuFe2As2. In another experiment, we discover that the magnetic order in CaFe2As2 can be melted selectively without significant effect on electrons in the other energy bands. These results provide two important conclusions; (i) magnetism in Fe-based systems may not be linked to the phase space occupied by other electrons and (ii) polarized pump excitation in a pump-probe experiment is a novel method to study orbital selective dynamics.