Evaluation of the coupling parameters of many-body interactions in Fe(110)

In order to clarify many-body interactions in ferromagnetic iron, we performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on a Fe(110) single crystal. We quantitatively analyzed the ARPES line shapes for a majority-spin band crossing the Fermi level $({E}_{F})$. The observed group velocity was reduced with respect to the band-structure calculation by a factor of 1/2.7, giving a coupling parameter due to the electron-electron interaction of ${\ensuremath{\lambda}}_{ee}=1.7\ifmmode\pm\else\textpm\fi{}0.1$. This suggests a strong electron correlation in $\text{Fe}\text{ }3d$, which is consistent with recent high-resolution ARPES results. The real and imaginary parts of the self-energy have been experimentally evaluated near ${E}_{F}$. The coupling parameter of the electron-phonon interaction was estimated to be ${\ensuremath{\lambda}}_{ep}=0.16\ifmmode\pm\else\textpm\fi{}0.02$, which is 1/10 of ${\ensuremath{\lambda}}_{ee}$. The effective-mass enhancement with respect to the band mass ${m}^{\ensuremath{\ast}}/{m}_{b}\ensuremath{\sim}1+{\ensuremath{\lambda}}_{ee}+{\ensuremath{\lambda}}_{ep}\ensuremath{\sim}3$ was, therefore, mainly caused by electron correlation.