Do you want to publish a course? Click here

Spin-wave excitations in the SDW state of iron pnictides: a comparison between the roles of interaction parameters

153   0   0.0 ( 0 )
 Added by Dheeraj Singh
 Publication date 2017
  fields Physics
and research's language is English




Ask ChatGPT about the research

We investigate the role of Hunds coupling in the spin-wave excitations of the ($pi, 0$) ordered magnetic state within a five-orbital tight-binding model for iron pnictides. To differentiate between the roles of intraorbital Coulomb interaction and Hunds coupling, we focus on the self-consistently obtained mean-field SDW state with a fixed magnetic moment obtained by using different sets of interaction parameters. We find that the Hunds coupling is crucial for the description of various experimentally observed characteristics of the spin-wave excitations including the anisotropy, energy-dependent behavior, and spin-wave spectral weight distribution.



rate research

Read More

We investigate the spin-wave excitations in the spin-density wave state of doped iron pnictides within a five-orbital model. We find that the excitations along ($pi, 0$)$rightarrow$($pi, pi$) are very sensitive to the doping whereas they do not exhibit a similar sensitivity along ($0, 0$) $rightarrow$ ($pi, 0$). Secondly, anisotropy in the excitations around ($pi, 0$) with an elliptical shape grows on moving towards the hole-doped region for low energy, whereas it decreases for the high-energy excitations on the contrary. Thirdly, spin-wave spectral weight shifts towards the low-energy region on moving away from zero doping. We find these features to be in qualitative agreement with the inelastic neutron-scattering measurements for the doped pnictides.
We investigate the impurity scattering induced quasiparticle interference in the ($pi, 0$) spin-density wave phase of the iron pnictides. We use a five orbital tight binding model and our mean field theory in the clean limit captures key features of the Fermi surface observed in angle-resolved photoemission. We use a t-matrix formalism to incorporate the effect of doping induced impurities on this state. The impurities lead to a spatial modulation of the local density of states about the impurity site, with a periodicity of $sim 8a_{{rm Fe}-{rm Fe}}$ along the antiferromagnetic direction. The associated momentum space quasiparticle interference pattern is anisotropic, with major peaks located at $sim (pm pi/4,0)$, consistent with spectroscopic imaging scanning tunneling microscopy. We trace the origin of this pattern to an elliptical contour of constant energy around momentum (0,0), with major axis oriented along the (0,1) direction, in the mean field electronic structure.
We calculate the expected finite frequency neutron scattering intensity based on the two-sublattice collinear antiferromagnet found by recent neutron scattering experiments as well as by theoretical analysis on the iron oxypnictide LaOFeAs. We consider two types of superexchange couplings between Fe atoms: nearest-neighbor coupling J1 and next-nearest-neighbor coupling J2. We show how to distinguish experimentally between ferromagnetic and antiferromagnetic J1. Whereas magnetic excitations in the cuprates display a so-called resonance peak at (pi,pi) (corresponding to a saddlepoint in the magnetic spectrum) which is at a wavevector that is at least close to nesting Fermi-surface-like structures, no such corresponding excitations exist in the iron pnictides. Rather, we find saddlepoints near (pi,pi/2) and (0,pi/2)(and symmetry related points). Unlike in the cuprates, none of these vectors are close to nesting the Fermi surfaces.
257 - C. Liu , D.-X. Yao , 2011
We study a two-orbital spin model to describe (pi,0) stripe antiferromagnetism in the iron pnictides. The double-spin model has an on-site Hundss coupling and inter-site interactions extending to second neighbors (inter- and intra-orbital) on the square lattice. Using a variational method based on a cluster decomposition, we optimize wave functions with up to 8 cluster sites (up to 2^16 variational parameters). We focus on the anomalously small ordered moments in the stripe state of the pnictides. To account for it, and large variations among different compounds, we show that the second-neighbor cross-orbital exchange constant should be ferromagnetic, which leads to partially hidden stripe order, with a moment that can be varied over a large range by small changes in the coupling constants. In a different parameter region, we confirm the existence of a canted state previously found in spin-wave theory. We also identify several other phases of the model.
188 - M. Naseska 2018
We report on systematic excitation-density dependent all-optical femtosecond time resolved study of the spin-density wave state in iron-based superconductors. The destruction and recovery dynamics are measured by means of the standard and a multi-pulse pump-probe technique. The experimental data are analyzed and interpreted in the framework of an extended three temperature model. The analysis suggests that the optical-phonons energy-relaxation plays an important role in the recovery of almost exclusively electronically driven spin density wave order.
comments
Fetching comments Fetching comments
Sign in to be able to follow your search criteria
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا