Department of Physics
Condensed Matter Seminar

Iron chalcogenide Fe_1+y(Te_1-xSe_x) is the simplified version of Fe-based superconductors [1,2] and has a unique antiferromagnetic (AFM) structure in the parent compound Fe_1+yTe [3,4]. In iron pnictide superconductor parent compounds, the in-plane AFM wavevector Q_AF is along the Fermi surface nesting direction (1/2,1/2) [5-7], while in Fe1+yTe, the in-plane component of Q_AF is (1/2,0), rotated 45° from the FS nesting direction. One central question in this burgeoning field is therefore whether the superconductivity in chalcogenides and pnictides have the same origin [8]. In this talk I will discuss the phase diagram of Fe_1+y(Te_1-xSe_x) that we have recently established. I will show that the magnetic soft mode evolving from the (1/2,0) AFM order leads to weak charge carrier localization, while bulk superconductivity occurs upon doping when the mode at (1/2,1/2) is dominant. Our results suggest that iron chalcogenide and pnictide superconductors share a common antiferromagnetic mode in their superconducting state.

References:

[1] F.C. Hsu et al., Proc. Natl. Acad. Sci. USA. 105, 14262 (2008).

[2] M.H. Fang et al., Phys. Rev. B 78, 224503 (2008).

[3] W. Bao et al., Phys. Rev. Lett. 102. 247001 (2009).

[4] S.L. Li et al., Phys. Rev. B 79, 054503 (2009).

[5] C. Cruz et al., Nature 453, 899 (2008).

[6] Q. Huang et al., Phys. Rev. Lett 101, 257003 (2008).

[7] J. Zhao et al., Phys. Rev. Lett. 101, 167203 (2008).

[8] A.V. Balatsky and D. Parker, Viewpoint, Physics 2, 59 (09)