Orbital selective spin waves in detwinned NaFeAs

摘要

The existence of orbital-dependent electronic correlations has been recognized as an essential ingredient to describe the physics of iron-based superconductors. NaFeAs, a parent compound of iron-based superconductors, exhibits a tetragonal-to-orthorhombic lattice distortion below T-s approximate to 60 K, forming an electronic nematic phase with two 90 degrees rotated (twinned) domains, and orders antiferromagnetically below T-N approximate to 42 K. We use inelastic neutron scattering to study spin waves in uniaxial pressure-detwinned NaFeAs. By comparing the data with combined density functional theory and dynamical mean-field theory calculations, we conclude that spin waves up to an energy scale of E-crossover approximate to 100 meV are dominated by d(yz)-d(yz) intraorbital scattering processes, which have the twofold (C-2) rotational symmetry of the underlying lattice. On the other hand, the spin wave excitations above Ecrossover, which have approximately fourfold (C-4) rotational symmetry, arise from the d(yz)-d(yz) intraorbital scattering that controls the overall magnetic bandwidth in this material. In addition, we find that the low-energy (E approximate to 6 meV) spin excitations change from approximate C-4 to C-2 rotational symmetry below a temperature T* (>T-s), while spin excitations at energies above E-crossover have approximate C-4 rotational symmetry and are weakly temperature dependent. These results are consistent with angle-resolved photoemission spectroscopy measurements, where the presence of a uniaxial strain necessary to detwin NaFeAs also raises the onset temperature T* of observable orbital-dependent band splitting to above T-s, thus supporting the notion of orbital selective spin waves in the nematic phase of iron-based superconductors.