Ilya Eremin

Magnetism, superconductivity, and pairing symmetry in iron-based superconductors

We analyze antiferromagnetism and superconductivity in novel Fe-based superconductors within the itinerant model of small electron and hole pockets near 0,0 and ,. We argue that the effective interactions in both channels logarithmically flow toward the same values at low energies; i.e., antiferromagnetism and superconductivity must be treated on equal footing. The magnetic instability comes first for equal sizes of the two pockets, but loses to superconductivity upon doping. The superconducting gap has no nodes, but changes sign between the two Fermi surfaces extended s-wave symmetry. We argue that the T dependencies of the spin susceptibility and NMR relaxation rate for such a state are exponential only at very low T, and can be well fitted by power laws over a wide T range below Tc.

Commensurate Spin Density Wave in LaFeAsO: A Local Probe Study

We present a detailed study on the magnetic order in the undoped mother compound LaFeAsO of the recently discovered Fe-based superconductor LaFeAsO1-xFx. In particular, we present local probe measurements of the magnetic properties of LaFeAsO by means of 57Fe Mössbauer spectroscopy and muon-spin relaxation in zero external field along with magnetization and resistivity studies. These experiments prove a commensurate static magnetic order with a strongly reduced ordered moment of 0.25(5)muB at the iron site below T(N)=138 K, well separated from a structural phase transition at T(S)=156 K. The temperature dependence of the sublattice magnetization is determined and compared to theory. Using a four-band spin density wave model both, the size of the order parameter and the quick saturation below T(N) are reproduced.

Theory of magnetic excitations in iron-based layered superconductors

Based on the effective four-band model we analyze the spin response in the normal and superconducting states of the Fe-pnictide superconductors. While the normal state spin excitations are dominated by the continuum of the interorbital antiferromagnetic fluctuations and the intraband spin density wave fluctuations, the unconventional superconductivity yields different feedback. The resonance peak in form of the well-defined spin exciton occurs {\it only} for the interband scattering at the antiferromagnetic momentum

Preemptive nematic order, pseudogap, and orbital order in the iron pnictides

{\bf Q}_{AFM}

A high-temperature ferromagnetic topological insulating phase by proximity coupling

for the

Magnetically driven suppression of nematic order in an iron-based superconductor

s_\pm

Magnetic degeneracy and hidden metallicity of the spin density wave state in ferropnictides

(extended s-wave) superconducting order parameter and it disappears rapidly for

Analysis of the resonance peak and magnetic coherence seen in inelastic neutron scattering of cuprate superconductors: A consistent picture with tunneling and conductivity data

{\bf q} < {\bf Q}_{AFM}

Incommensurate itinerant antiferromagnetic excitations and spin resonance in the FeTe0.6Se0.4 superconductor

. The resonance feature is extremely weak for the

Interplay of magnetic and structural transitions in iron-based pnictide superconductors

d_{x^2 -y^2}