TY - JOUR
T1 - Impact of dynamic orbital correlations on magnetic excitations in the normal state of iron-based superconductors
AU - Lee, Wei Cheng
AU - Lv, Weicheng
AU - Tranquada, J. M.
AU - Phillips, Philip W.
PY - 2012/9/14
Y1 - 2012/9/14
N2 - We show here that orbital degrees of freedom produce a distinct signature in the magnetic excitation spectrum of iron-based superconductors above the magnetic ordering temperature. Because d xz and d yz orbitals are strongly connected with Fermi surface topology, the nature of magnetic excitations can be modified significantly due to the presence of either static or fluctuating orbital correlations. Within a five-orbital itinerant model, we show that static orbital order generally leads to an enhancement of commensurate magnetic excitations even when the original Fermi surface lacks nesting at (π,0) or (0,π). When long-range orbital order is absent, Gaussian fluctuations beyond the standard random-phase approximation capture the effects of fluctuating orbital correlations on the magnetic excitations. We find that commensurate magnetic excitations can also be enhanced if the orbital correlations are strong. Our results offer a natural explanation for the incommensurate-to-commensurate transformation observed in a recent neutron scattering measurement (Xu, arXiv:1201.4404), and we propose that this unusual transformation is an important signature to distinguish orbital from spin physics in the normal state of pnictides. Implications for the magnetic and superconducting states are discussed.
AB - We show here that orbital degrees of freedom produce a distinct signature in the magnetic excitation spectrum of iron-based superconductors above the magnetic ordering temperature. Because d xz and d yz orbitals are strongly connected with Fermi surface topology, the nature of magnetic excitations can be modified significantly due to the presence of either static or fluctuating orbital correlations. Within a five-orbital itinerant model, we show that static orbital order generally leads to an enhancement of commensurate magnetic excitations even when the original Fermi surface lacks nesting at (π,0) or (0,π). When long-range orbital order is absent, Gaussian fluctuations beyond the standard random-phase approximation capture the effects of fluctuating orbital correlations on the magnetic excitations. We find that commensurate magnetic excitations can also be enhanced if the orbital correlations are strong. Our results offer a natural explanation for the incommensurate-to-commensurate transformation observed in a recent neutron scattering measurement (Xu, arXiv:1201.4404), and we propose that this unusual transformation is an important signature to distinguish orbital from spin physics in the normal state of pnictides. Implications for the magnetic and superconducting states are discussed.
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U2 - 10.1103/PhysRevB.86.094516
DO - 10.1103/PhysRevB.86.094516
M3 - Article
AN - SCOPUS:84866393005
VL - 86
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 0163-1829
IS - 9
M1 - 094516
ER -