Origin of the spin density wave instability in AFe2As2 (A=Ba,Sr) as revealed by optical spectroscopy.
We performed optical spectroscopy measurement on single crystals of BaFe2As2 and SrFe2As2, the parent compounds of FeAs-based superconductors. Both are found to be quite metallic with fairly large plasma frequencies at high temperature. Upon entering the spin-density-wave state, the formation of partial energy gaps was clearly observed with the surprising presence of two different energy scales. A large part of the Drude component was removed by the gapping of Fermi surfaces. Meanwhile, the carrier scattering rate was even more dramatically reduced. We elaborate that the spin-density-wave instability is more likely to be driven by the Fermi surface nesting of itinerant electrons than a local-exchange mechanism.
Hu
W Z
WZ
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Dong
J
J
Li
G
G
Li
Z
Z
Zheng
P
P
Chen
G F
GF
Luo
J L
JL
Wang
N L
NL