Abstract
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.
Original language | English |
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Article number | 2874 |
Journal | Nature Communications |
Volume | 4 |
DOIs | |
State | Published - Dec 4 2013 |
Funding
The single crystal growth and neutron scattering work at Rice/UTK is supported by the US DOE BES under Grant No. DE-FG02-05ER46202. Work at IOP is supported by the MOST of China 973 programs (2012CB821400, 2011CBA00110) and NSFC. The LDA + DMFT computations were made possible by an Oak Ridge leadership computing facility director discretion allocation to Rutgers. The work at Rutgers is supported by DOE BES DE-FG02-99ER45761 (G.K.) and NSF-DMR 0746395 (K.H.). T.A.M. acknowledges the Center for Nanophase Materials Sciences, which is sponsored at ORNL by the Scientific User Facilities Division, BES, US DOE.