Doping dependence of spin excitations and its correlations with high-temperature superconductivity in iron pnictides

• Published in: Nature communications Vol. 4; no. 1; p. 2874
• Main Authors: Wang, Meng, Zhang, Chenglin, Lu, Xingye, Tan, Guotai, Luo, Huiqian, Song, Yu, Wang, Miaoyin, Zhang, Xiaotian, Goremychkin, E.A., Perring, T.G., Maier, T.A., Yin, Zhiping, Haule, Kristjan, Kotliar, Gabriel, Dai, Pengcheng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04-12-2013; Nature Publishing Group; Nature Pub. Group
• Subjects: 639/766/119/1003; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Electrons; Energy; Humanities and Social Sciences; multidisciplinary; Physics; Science; science & technology; Science (multidisciplinary); Temperature; Beijing China; United States > US; China; Tennessee
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms3874

High-temperature superconductivity in iron pnictides occurs when electrons and holes are doped into their antiferromagnetic parent compounds. Since spin excitations may be responsible for electron pairing and superconductivity, it is important to determine their electron/hole-doping evolution and connection with superconductivity. Here we use inelastic neutron scattering to show that while electron doping to the antiferromagnetic BaFe
2
As
2
parent compound modifies the low-energy spin excitations and their correlation with superconductivity (<50 meV) without affecting the high-energy spin excitations (>100 meV), hole-doping suppresses the high-energy spin excitations and shifts the magnetic spectral weight to low-energies. In addition, our absolute spin susceptibility measurements for the optimally hole-doped iron pnictide reveal that the change in magnetic exchange energy below and above
T
c
can account for the superconducting condensation energy. These results suggest that high-
T
c
superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons.
Spin excitations are believed by many to play an important role in the emergence of superconductivity in the iron pnictides. Neutron scattering results collected by Wang
et al.
suggest that strong coupling between itinerant electrons and spin excitations is necessary for superconductivity in these materials.