研究目的
Investigating the electronic structure and superconducting gap of Sr1?yCayFe2(As1?xPx)2 to understand the effects of structural anisotropy on Fermi surfaces and gap structures, and to explore the pairing mechanisms in iron-based superconductors.
研究成果
The study revealed that the structural anisotropy significantly affects the FS topology and SC gap structures in Sr1?yCayFe2(As1?xPx)2. The observed gap minimum on the dxy electron FS and isotropic gaps around other high symmetry points suggest contributions from both spin and orbital fluctuations to the superconductivity. The results support theories incorporating orbital fluctuation in addition to spin fluctuation for explaining the SC mechanism in this system.
研究不足
The ARPES spectra are affected by the kz broadening effect due to the short escape depth of photoelectrons, which may influence the estimation of FS shapes and SC gaps. The discrepancy between experimental results and band calculations suggests constraints not accounted for in the calculations.
1：Experimental Design and Method Selection:
Angle-resolved photoemission spectroscopy (ARPES) was used to investigate the electronic structure. The methodology included the use of synchrotron radiation light for high-resolution measurements.
2：Sample Selection and Data Sources:
Single crystals of Sr1?yCayFe2(As1?xPx)2 were synthesized by the self-flux method and annealed to minimize disorder effects. ARPES measurements were conducted at BL 7U and BL 5U in UVSOR-III Synchrotron.
3：List of Experimental Equipment and Materials:
Instruments included synchrotron radiation light sources, MBS A1 analyzer, and ultrahigh vacuum chambers. Materials included single crystals of the specified composition.
4：Experimental Procedures and Operational Workflow:
Samples were cleaved in-situ at 12 K in ultrahigh vacuum. Calibration of the Fermi level was achieved by referring to gold spectra. Data were collected over approximately 6 hours per set.
5：Data Analysis Methods:
Data were analyzed using symmetrized energy-distribution curves (EDCs) and momentum distribution curves (MDCs). The SC gap values were estimated using a phenomenological SC spectral function.
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