Strong coupling s-wave superconductivity in MgB2: 11111111B-NMR Study of MgB2 and Al-dopedMgB2

Hisashi Kotegawa, Kenji Ishida, Yoshio Kitaoka, Takahiro Muranaka, Norimasa Nakagawa, Hiroyuki Takagiwa, Jim Akimitsu

Research output: Contribution to journalArticle

Abstract

We have measured nuclear spin-lattice relaxation time, T1 of 11B in MgB2 and Al-doped MgB 2-T1T = const, behavior is observed in the normal state, indicating the absence of strong magnetic correlation. In the superconducting (SC) state of MgBg, 1/T1 shows a tiny coherence peak just below Tg and decreases exponentially with a large SC gap of 2A/kBTc ∼ 5. These results suggest that M gB2 is a strong coupling s-wave superconductor. As Al 3+ is doped into Mg2+ site, 1/T1T which is proportional to the square of the density of states (DOS) decreases. The variation of Tc against the DOS deduced from 1/T1T is fitted by McMillan equation, and the Debye frequency ω and the electron-phonon coupling constant A were estimated as ∼ 700 K and ∼ 0.87, respectively. Both are in good agreement with the values from theoretical works. The high-Tc superconductivity in MgB2 is considered to occur through strong coupling between electrons and high frequency-phonon.

Original languageEnglish
Pages (from-to)332-334
Number of pages3
Journaljournal of the physical society of japan
Volume71
Issue numberSUPPL.
DOIs
Publication statusPublished - Jan 1 2002
Externally publishedYes

Keywords

  • Al-doped MB
  • MB
  • McMillan equation
  • NMR
  • S-wave superconductivity

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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