Observation of iron d-orbitals modifications in superconducting FeSe by Raman spectra study
Abstract
We have studied the Raman spectra of superconducting FeSe and non-superconducting Cu-doped FeSe crystals at different temperatures. The spectral range covers the phonon modes at low frequency regime to electronic Raman scattering at high frequency regime, up to 2000 cm-1. A hardening in frequency of B1g mode, which is related to the spin-phonon coupling is observed. At high frequency region, our results on superconducting FeSe crystal show that the dzx and dyz orbitals of Fe split at ∼130 K and then become closer to achieve balance as temperature decreases. This result indicates that a modification of d-orbital electron state of iron happens at temperature much higher than the structural transition, implicating a precursor order in iron-based superconductor. In comparison with non-superconducting Cu0.03Fe0.97Se crystal, our observations suggest that the orbital modification could be an important clue for understanding the mechanism of superconductivity in iron-based superconductors.
- Publication:
-
Physica C Superconductivity
- Pub Date:
- September 2018
- DOI:
- 10.1016/j.physc.2018.02.041
- Bibcode:
- 2018PhyC..552...61H
- Keywords:
-
- Raman spectroscopy;
- Phonon modes;
- FeSe superconductor;
- Structural distortion