Direct evidence of uneven dxz and dyz orbital occupation in the superconducting state of iron pnictide

Damian Rybicki; Marcin Sikora; Joanna Stępień; Łukasz Gondek; Kamil Goc; Tomasz Strączek; Michał Jurczyszyn; Czesław Kapusta; Zbigniew Bukowski; Michał Babij; Marcin Matusiak; Marcin Zając

doi:10.1103/PhysRevB.102.195126

Direct evidence of uneven dxz and dyz orbital occupation in the superconducting state of iron pnictide

Damian Rybicki, Marcin Sikora, Joanna Stępień, Łukasz Gondek, Kamil Goc, Tomasz Strączek, Michał Jurczyszyn, Czesław Kapusta, Zbigniew Bukowski, Michał Babij, Marcin Matusiak, Marcin Zając

DOI 10.1103/PhysRevB.102.195126 · Physical Review B

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Abstract

The origin of nematicity and its relation to superconductivity in iron pnictide high-temperature superconductors remains unclear. One of its possible sources is the uneven occupation of Fe dxz and dyz orbitals. Here, by using x-ray linear dichroism technique, we show that such an imbalance is present in Eu(Fe1−xCox)2As2 single crystals deep in the tetragonal phase and also in the superconducting state, where we find that the dxz orbital has a higher occupation as indicated by an x-ray linear dichroism magnitude of 1.5%. Our result shows the importance of orbital polarization in the theoretical description of nematicity and superconductivity, particularly for determination of the superconducting gap symmetry, which is affected by orbital fluctuations.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
EuFe1.8Co0.2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	10	Pressure not reported	unknown