The spatial distributions of large gap-like structure on Fe(Se,Te) single crystals observed by STM/STS

• Published in: Physica. C, Superconductivity Superconductivity, 2015-11, Vol.518, p.23-27
• Main Authors: Sugimoto, Akira, Sakai, Yuta, Nagasaka, Kouhei, Ekino, Toshikazu
• Format: Article
• Language: English
• Subjects: FeSe1−xTex; Iron chalcogenide superconductors; STM/STS; Tunneling spectroscopy
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2015.04.007

•The nanoscale large gap VPG and small gap Δ maps of Fe(Se,Te) were observed by STS.•The STM topography shows clear atomic structure of ∼0.38nm spacing.•The average of large gaps is |VPG|∼305mV with σ∼48mV.•The smallest gap magnitude Δ∼7meV was estimated by fitting curve. The nanoscale spatial distributions of large gap-like structure on superconducting FeSe1−xTex were investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The STM topography shows regular atomic lattice arrangements with the lattice spacing ∼0.38nm, together with the randomly distributed large spots due to the excess Fe atoms. From the STS measurements, the small gap structures of Δ∼7meV were partly observed. On the other hand, the high-bias dI/dV curves exhibit the broad peak structures at the negative biases of VPG=−200 to −400mV in the measured whole surface area. The average of these large gaps is |VPGave|∼305mV with the standard deviation of σ∼48mV. The spatial distributions of the VPG exhibit the domain structures consisting of the relatively smaller gaps (