title: Itinerancy-enhanced quantum fluctuation of magnetic moments in iron-based superconductors.
abstract: We investigate the influence of itinerant carriers on the dynamics and fluctuation of local moments in Fe-based superconductors, via linear spin-wave analysis of a spin-fermion model containing both itinerant and local degrees of freedom. Surprisingly, against the common lore, instead of enhancing the (π,0) order, itinerant carriers with well-nested Fermi surfaces are found to induce a significant amount of spatial and temporal quantum fluctuation that leads to the observed small ordered moment. Interestingly, the underlying mechanism is shown to be an intrapocket nesting-associated long-range coupling rather than the previously believed ferromagnetic double-exchange effect. This challenges the validity of ferromagnetically compensated first-neighbor coupling reported from short-range fitting to the experimental dispersion, which turns out to result instead from the ferro-orbital order that is also found instrumental in stabilizing the magnetic order.
authors.affiliation: State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.|CMPMSD, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Tam
authors.affiliation: State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.
authors.forename: Dao-Xin
authors.initials: DX
authors.lastname: Yao
authors.affiliation: CMPMSD, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.|Physics Department, State University of New York, Stony Brook, New York 11790, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Ku