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.
|頁（從 - 到）||61-63|
|期刊||Physica C: Superconductivity and its applications|
|出版狀態||已發佈 - 2018 9月 15|
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