Department Spin and Topology in Quantum Materials

Correlation effects in the spin-dependent electronic structure of iron, cobalt and nickel

This research activity aims at comparing the spin-dependent electronic structure of ferromagnets to their description by modern theoretical models developed mainly for strongly correlated systems, and it is the question whether these models resolve the well-known discrepancies between experiment and local-spin-density calculations. This comparison takes into account matrix elements as well as surface states via a 1-step treatment of the photoemission process. The comparison has been done for Fe (see figure), Co, Ni, and permalloy and the central result is that the theoretical description is still insufficient.

The figure shows spin-dependent electron correlation in Fe measured from the Fe(110) surface in normal emission at various photon energies (x gives the corresponding perpendicular wave vector k in units of the N distance). (a,b) Experimental data and (c,d) dynamical mean-field theory with 1-step photoemission calculation. (a,c) p- and (b,d) s-polarized light. Even these state-of-the-art treatments of electron correlation do not give a satisfactory description of real and imaginary parts of the self energy. 

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J. Sánchez-Barriga et al. Phys. Rev. Lett, 121, 267201 (2018).}