Observation of a Superconducting Gap in Boron-Doped Diamond by Laser-Excited Photoemission Spectroscopy

K. Ishizaka, R. Eguchi, S. Tsuda, T. Yokoya, A. Chainani, T. Kiss, T. Shimojima, T. Togashi, S. Watanabe, C.-T. Chen, C. Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi, H. Kawarada, and S. Shin

Phys. Rev. Lett. 98, 047003 – Published 23 January 2007

Abstract

We investigate the temperature ( $T$ )-dependent low-energy electronic structure of a boron-doped diamond thin film using ultrahigh resolution laser-excited photoemission spectroscopy. We observe a clear shift of the leading edge below $T = 11 K$ , indicative of a superconducting gap opening ( $Δ \sim 0.78 meV$ at $T = 4.5 K$ ). The gap feature is significantly broad and a well-defined quasiparticle peak is lacking even at the lowest temperature of measurement ( $= 4.5 K$ ). We discuss our results in terms of disorder effects on the normal state transport and superconductivity in this system.

Received 4 April 2006

DOI:https://doi.org/10.1103/PhysRevLett.98.047003

Authors & Affiliations

K. Ishizaka¹, R. Eguchi², S. Tsuda¹, T. Yokoya³, A. Chainani², T. Kiss⁴, T. Shimojima¹, T. Togashi², S. Watanabe¹, C.-T. Chen⁵, C. Q. Zhang⁵, Y. Takano⁶, M. Nagao⁶, I. Sakaguchi⁶, T. Takenouchi⁷, H. Kawarada⁷, and S. Shin^1,2

¹Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
²The Institute of Physical and Chemical Research (RIKEN), Sayo-gun, Hyogo 679-5143, Japan
³The Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
⁴The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan
⁵Beijing Center for Crystal R&D, Chinese Academy of Science, Zhongguancun, Beijing 100080, China
⁶National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
⁷School of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan

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Issue

Vol. 98, Iss. 4 — 26 January 2007

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