Tunneling break-junction spectroscopy on the superconductor NdFeAs(O0.9F0.1)

✍ Scribed by Toshikazu Ekino; Akira Sugimoto; Hirotaka Okabe; Kazuhiro Shohara; Ryuichi Ukita; Jun Akimitsu; Alexander M. Gabovich

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 165 KB
• Volume: 470
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2009.10.079

✦ Synopsis

Tunnel break-junction method has been adopted to study polycrystalline samples of iron-oxypnictide superconductor NdFeAs(O 0.9 F 0.1 ) with T c ¼ 48 K. Measurements were carried out at 4.2 K. Break-junction (BJ) conductance versus voltage curves showed gap-edge peaks with the peak-to-peak distances V pÀp ¼ 4D=e ¼ 28-40 mV at 4.2 K, where 2DðTÞ is the superconducting energy gap, e > 0 is the elementary charge. This yields 2Dð0Þ ¼ 14-20 meV, so that the gap ratio 2Dð0Þ=k B T c is about 4:1 AE 0:7; k B being the Boltzmann constant. This ratio implies strong-coupling superconductivity in the framework of Bardeen-Cooper-Schrieffer theory, being, however, much smaller than that for high-T c copper oxides. This suggests a significant difference in the pairing mechanism between those classes of materials.