From (π,0) magnetic order to superconductivity with (π,π) magnetic resonance in Fe1.02Te1−xSex

Abstract

The iron chalcogenide Fe(1+y)(Te(1-x)Se(x)) is structurally the simplest of the Fe-based superconductors. Although the Fermi surface is similar to iron pnictides, the parent compound Fe(1+y)Te exhibits antiferromagnetic order with an in-plane magnetic wave vector (pi,0) (ref. 6). This contrasts the pnictide parent compounds where the magnetic order has an in-plane magnetic wave vector (pi,pi) that connects hole and electron parts of the Fermi surface. Despite these differences, both the pnictide and chalcogenide Fe superconductors exhibit a superconducting spin resonance around (pi,pi) (refs 9, 10, 11). A central question in this burgeoning field is therefore how (pi,pi) superconductivity can emerge from a (pi,0) magnetic instability. Here, we report that the magnetic soft mode evolving from the (pi,0)-type magnetic long-range order is associated with weak charge carrier localization. Bulk superconductivity occurs as magnetic correlations at (pi,0) are suppressed and the mode at (pi, pi) becomes dominant for x>0.29. Our results suggest a common magnetic origin for superconductivity in iron chalcogenide and pnictide superconductors.

Competition between commensurate and incommensurate magnetic ordering in Fe1+yTe

“…It was grown by the Bridgman technique, and the exarXiv:1111.4236v2 [cond-mat.supr-con] 4 Apr 2012 cess iron content was determined by Patterson refinement of single-crystal x-ray diffraction data to be y = 0.08. The Néel temperature was defined as the steepest slope of the magnetic Bragg peak intensity with temperature, was found to be T N = 67.5 K, consistent with other reports [9][10][11] for this value of y. The crystal structure at room temperature is tetragonal (space group 129, P4/nmm) with lattice constants a = b = 3.823(3)Å and c = 6.282(6)Å.…”

Antiferromagnetic order and spin dynamics in iron-based superconductors

“…For the nonsuperconducting Fe 1+y Te 0.73 Se 0.27 , spin excitations at low energies (E = 10 ± 1, 22 ± 3 meV) peak at transversely incommensurate positions from (0.5, 0.5) [Figs. 23(a) sults are similar to spin excitations in electron-doped iron pnictides , suggesting that superconductivity in iron chalcogenides only affects low-energy spin excitations and has commensurate spin excitations consistent with the hole and electron Fermi surface nesting (Chi et al, 2011;Liu et al, 2010). In iron pnictide and iron chalcogenide superconductors, the neutron spin resonance is believed to arise from quasiparticle excitations between the hole and electron Fermi pockets near the Γ and M points, respectively Mazin, 2010).…”

“…the expense of the spin excitations associated with the AF nonsuperconducting parent compound (Chi et al, 2011;Liu et al, 2010;Xu et al, 2010). Figure 23 compares the wave vector dependence of spin excitations at different energies within the (H, K) plane for nonsuperconducting Fe 1+y Te 0.73 Se 0.27 and superconducting Fe 1+y Te 0.51 Se 0.49 .…”

Electronic structure of FeS

“…[13,24], and the phase diagram, including the Tcs for FeSe1−xTex and FeSe1−xSx were taken from Refs. [10,15,38,39]. Two regions of the SC dome marked by black dashed lines are inferred based on interpolation, in the absence of any report on these substitution.…”