Phys. Rev. B 67, 100509 (2003) [4 pages]Superconducting characteristics in electron-doped layered hafnium nitride: 15N isotope effect studies |
Hideki Tou1,2 *, Yutaka Maniwa2,3, and Shoji Yamanaka4
1Department of Quantum Matter, AdSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
2Department of Physics, Tokyo Metropolitan University, Minami-osawa, Hachi-oji Tokyo 192-0397, Japan
3CREST, Japan Science and Technology Corporation (JST), Toshima-ku, Tokyo 171-0031, Japan
4Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan
Received 21 January 2003; published 31 March 2003
We report 15N nuclear magnetic resonance (NMR) and the nitrogen-isotope effect studies on c-axis oriented sample of Li-doped HfNCl with superconducting transition temperature Tc∼25.5 K. 15N NMR Knight shift decreases toward zero below Tc, giving evidence that the pairing symmetry is an even-parity spin singlet, and that the nitrogen site plays an important role in the occurrence of superconductivity. A nitrogen isotope shift is found to be quite small, ΔTc∼0.1 K (αN=0.07±0.02), which cannot reproduce such a high Tc within the traditional BCS framework.
©2003 The American Physical Society
URL: http://link.aps.org/abstract/PRB/v67/e100509
DOI: 10.1103/PhysRevB.67.100509
PACS: 74.70.-b, 74.25.Ha, 76.60.Cq
* Email address: tou@hiroshima-u.ac.jp
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