Suppression of electronic correlations by chemical pressure from FeSe to FeS
Phys. Rev. B 96, 121103(R) (2017) American Physical Society (2017)
Abstract:
Iron-based chalcogenides are complex superconducting systems in which orbitally-dependent electronic correlations play an important role. Here, using high-resolution angle-resolved photoemission spectroscopy, we investigate the effect of these electronic correlations outside the nematic phase in the tetragonal phase of superconducting FeSe1-xSx (x = 0; 0:18; 1). With increasing sulfur substitution, the Fermi velocities increase significantly and the band renormalizations are suppressed towards a factor of 1.5-2 for FeS. Furthermore, the chemical pressure leads to an increase in the size of the quasi-two dimensional Fermi surface, compared with that of FeSe, however, it remains smaller than the predicted one from first principle calculations for FeS. Our results show that the isoelectronic substitution is an effective way to tune electronic correlations in FeSe1-xSx, being weakened for FeS with a lower superconducting transition temperature. This suggests indirectly that electronic correlations could help to promote higher-Tc superconductivity in FeSe.Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe
PHYSICAL REVIEW B 95:8 (2017) ARTN 081106
de Haas–van Alphen study of role of4 f electrons in antiferromagneticCeZn 11 as compared to its nonmagnetic analogLaZn 11
Physical Review B American Physical Society (APS) 94:23 (2016) 235103
Evidence for unidirectional nematic bond ordering in FeSe
Physical Review B American Physical Society 94:20 (2016)
Abstract:
The presence of dxz−dyz orbital ordering is often considered a hallmark of the nematic phase of Fe-based superconductors, including FeSe, but the details of the order parameter remain controversial. Here, we report a high-resolution angle-resolved photoemission spectroscopy study of single crystals of FeSe, accounting for the photon-energy dependence and making a detailed analysis of the temperature dependence. We find that the hole pocket undergoes a fourfold-symmetry-breaking distortion in the nematic phase below 90 K, but, in contrast, the changes to the electron pockets do not require fourfold symmetry breaking. Instead, there is an additional separation of the existing dxy and dxz/yz bands, which themselves are not split within resolution. These observations lead us to propose a scenario of “unidirectional nematic bond ordering” to describe the low-temperature electronic structure of FeSe, supported by good agreement with ten-orbital tight-binding model calculations.Evidence for unidirectional nematic bond ordering in FeSe
Physical Review B - Condensed Matter and Materials Physics American Physical Society (2016)