15 research outputs found
Impurity-induced smearing of the spin resonance peak in Fe-based superconductors
The spin resonance peak in the iron-based superconductors is observed in
inelastic neutron scattering experiments and agrees well with predicted results
for the extended s-wave () gap symmetry. On the basis of four-band and
three-orbital tight binding models we study the effect of nonmagnetic disorder
on the resonance peak. Spin susceptibility is calculated in the random phase
approximation with the renormalization of the quasiparticle self-energy due to
the impurity scattering in the static Born approximation. We find that the spin
resonance becomes broader with the increase of disorder and its energy shifts
to higher frequencies. For the same amount of disorder the spin response in the
state is still distinct from that of the state.Comment: 4 pages, 2 figure
Spin resonance peak in Fe-based superconductors with unequal gaps
We study the spin resonance in the superconducting state of iron-based materials within multiband models with two unequal gaps, ΞL and ΞS, on different Fermi-surface pockets. We show that, due to the indirect nature of the gap entering the spin susceptibility at the nesting wave vector Q, the total gap ΞΛ in the bare susceptibility is determined by the sum of gaps on two different Fermi-surface sheets connected by Q. For the Fermi-surface geometry characteristic of most iron pnictides and chalcogenides, the indirect gap is either ΞΛ=ΞL+ΞS or ΞΛ=2ΞL. In the s++ state, spin excitations below ΞΛ are absent unless additional scattering mechanisms are assumed. The spin resonance appears in the sΒ± superconducting state at frequency ΟRβ€ΞΛ. Comparison with available inelastic neutron-scattering data confirms that what is seen is the true spin resonance and not a peak inherent to the s++ state
Impurity-Induced Smearing of the Spin Resonance Peak in Fe-Based Superconductors
Π’Π΅ΠΊΡΡ ΡΡΠ°ΡΡΠΈ Π½Π΅ ΠΏΡΠ±Π»ΠΈΠΊΡΠ΅ΡΡΡ Π² ΠΎΡΠΊΡΡΡΠΎΠΌ Π΄ΠΎΡΡΡΠΏΠ΅ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΎΠΉ ΠΆΡΡΠ½Π°Π»Π°.The spin resonance peak in the iron-based superconductors is observed in inelastic neutron scattering experiments and agrees well with predicted results for the extended s-wave (sΒ±) gap symmetry. On the basis of four-band and three-orbital tight-binding models we study the effect of nonmagnetic disorder on the resonance peak. Spin susceptibility is calculated in the random-phase approximation with the renormalization of the quasiparticle self-energy due to the impurity scattering in the static Born approximation. We find that the spin resonance becomes broader with the increase of disorder and its energy shifts to higher frequencies. For the same amount of disorder the spin response in the sΒ± state is still distinct from that of the s++ state
Uniform Impurity Scattering in Two-Band sΒ± and s++ Superconductors
Π’Π΅ΠΊΡΡ ΡΡΠ°ΡΡΠΈ Π½Π΅ ΠΏΡΠ±Π»ΠΈΠΊΡΠ΅ΡΡΡ Π² ΠΎΡΠΊΡΡΡΠΎΠΌ Π΄ΠΎΡΡΡΠΏΠ΅ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΎΠΉ ΠΆΡΡΠ½Π°Π»Π°.The sΒ± and s++ models for the superconducting state are subject of intense studies regarding Fe-based superconductors. Depending on the parameters, disorder may leave intact or suppress T c in these models. Here, we study the special case of disorder with equal values of intra- and interband impurity potentials in the two-band sΒ± and s++ models. We show that this case can be considered as an isolated point and Tc there has maximal damping for a wide range of parameters
Spin resonance peak in Fe-based superconductors with unequal gaps
We study the spin resonance in the superconducting state of iron-based materials within multiband models with two unequal gaps, ΞL and ΞS, on different Fermi-surface pockets. We show that, due to the indirect nature of the gap entering the spin susceptibility at the nesting wave vector Q, the total gap ΞΛ in the bare susceptibility is determined by the sum of gaps on two different Fermi-surface sheets connected by Q. For the Fermi-surface geometry characteristic of most iron pnictides and chalcogenides, the indirect gap is either ΞΛ=ΞL+ΞS or ΞΛ=2ΞL. In the s++ state, spin excitations below ΞΛ are absent unless additional scattering mechanisms are assumed. The spin resonance appears in the sΒ± superconducting state at frequency ΟRβ€ΞΛ. Comparison with available inelastic neutron-scattering data confirms that what is seen is the true spin resonance and not a peak inherent to the s++ state
Uniform Impurity Scattering in Two-Band sΒ± and s++ Superconductors
Π’Π΅ΠΊΡΡ ΡΡΠ°ΡΡΠΈ Π½Π΅ ΠΏΡΠ±Π»ΠΈΠΊΡΠ΅ΡΡΡ Π² ΠΎΡΠΊΡΡΡΠΎΠΌ Π΄ΠΎΡΡΡΠΏΠ΅ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΎΠΉ ΠΆΡΡΠ½Π°Π»Π°.The sΒ± and s++ models for the superconducting state are subject of intense studies regarding Fe-based superconductors. Depending on the parameters, disorder may leave intact or suppress T c in these models. Here, we study the special case of disorder with equal values of intra- and interband impurity potentials in the two-band sΒ± and s++ models. We show that this case can be considered as an isolated point and Tc there has maximal damping for a wide range of parameters