Superconducting Properties of InN with Low Carrier Density near the Mott Transition

• Published in: Journal of the Physical Society of Japan Vol. 81; no. 4; p. 1
• Main Authors: Inushima, Takashi, Maude, Duncan K, Lu, Hai, Schaff, William J, Iizuka, Takuya, Kimura, Shin-ichi, Yamamoto, Akio, Fukui, Kazutoshi
• Format: Journal Article
• Language: English
• Published: Tokyo The Physical Society of Japan 01-04-2012
• Subjects: Carrier density; Conduction band; Critical field (superconductivity); Electrical conduction; Electrons; Fluid flow; Meissner effect; Melting; Physics; Superconductivity; Superconductors; Vortices
• ISSN: 0031-9015; 1347-4073

We report on two types of superconductivity of InN with low carrier density near the Mott transition. One type has a superconducting transition which occurs in the electrical conduction and in Meissner effect simultaneously, which obscures the upper critical field. The upward curvature of the vortex-melting field versus temperature is similar to that observed in high T c superconductors. The other is a BCS-type superconductivity with the superconducting gap similar to that of metal In. The superconducting phase is a glassy vortex solid and melts by thermal fluctuation of vortices caused by large penetration length. The structure of the Fermi surface is investigated measuring magneto-plasma reflection and magneto-resistance at low temperatures. The results show that there are two types of electrons in the conduction band. In order to explain the two types of superconductivity, a model of residual carrier caused by a strong s - d coupling is presented.