Effects of aging processes at the surface of the superconductor β − FeSe

LANOËL, L.; AMIGÓ, M. L.; VILLAFUERTE, M.; ROZAS, G.; NIEVA, G.; CRIVILLERO, M. V. ALE; BRIDOUX, G.; BRUCHHAUSEN, A. E.; HOFER, J. A.; BENGIÓ, S.

Physical Review B

American Physical Society

Año: 2022 vol. 106

2469-9950

This work reports a complete analysis of surface degradation in β-FeSe single crystals; which includes the11 dependence on aging and temperature of Raman spectra, electrical transport resistivity, and XPS depth profiling12 characterization. All measurements are consistent with the emergence of clusters of Se and the presence of FeOx13 in the surface of the crystals. The vibrational modes of the Se clusters are coupled to the β-FeSe ones as seen14 in the structural transition. Moreover, this degraded surface can behave like a quasi-two-dimensional layer, as15 supported by a theoretical model and also consistent with Raman spectra. While the degradation of thin films of16 β-FeSe in air is widely known, with a corresponding loss of the superconducting properties, in single crystals17 with aged surfaces we observe an enhancement of the superconducting properties.