Spin gap and resonance at the nesting wave vector in superconducting FeSe_{0.4}Te_{0.6}.
Neutron scattering is used to probe magnetic excitations in FeSe_{0.4}Te_{0.6} (T_{c} = 14 K). Low energy spin fluctuations are found with a characteristic wave vector (1/21/2L) that corresponds to Fermi surface nesting and differs from Q_{m} = (delta01/2) for magnetic ordering in Fe_{1+y}Te. A spin resonance with variant Planck's over 2piOmega_{0} = 6.51(4) meV approximately 5.3k_{B}T_{c} and variant Planck's over 2piGamma = 1.25(5) meV develops in the superconducting state from a normal state continuum. We show that the resonance is consistent with a bound state associated with s_{+/-} superconductivity and imperfect quasi-2D Fermi surface nesting.
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Yiming
Y
Qiu
Wei
W
Bao
Y
Y
Zhao
Collin
C
Broholm
V
V
Stanev
Z
Z
Tesanovic
Y C
YC
Gasparovic
S
S
Chang
Jin
J
Hu
Bin
B
Qian
Minghu
M
Fang
Zhiqiang
Z
Mao