Negative isotope effect of a BCS-like gap; an inelastic light scattering study

In-Sang Yang; M. V. Klein; S. Bud'ko; P. C. Canfield

Negative isotope effect of a BCS-like gap; an inelastic light scattering study

Superconductivity 2007-05-23 v1

Authors: In-Sang Yang , M. V. Klein , S. Bud'ko , P. C. Canfield

Abstract

In a prior study of the boron isotope effect on the transition temperature ( $T_c$ ) of $R$ Ni $_2$ B $_2$ C ( $R$ = Y, Lu) system, a positive isotope effect was observed, e.g., $T_{c}(^{10}B)> T_{c}(^{11}B)$ . BCS theory predicts that the superconducting gap at zero temperature ( $\Delta_0$ ) is proportional to $T_c$ . Therefore, the gap should also show a positive boron isotope effect. On the contrary, in an inelastic light scattering study, we report a negative boron isotope effect on the energy $\Omega$ of the gap-like feature in B $_{2g}$ symmetry, e.g., $\Omega(^{10}B)< \Omega(^{11}B)$ . The origin of the effect is discussed in terms of selective probing of a non-conventional electron-phonon interaction on part of the Fermi surface, probably near the X point in the Brillouin zone.

Keywords

BCS theory isotope effect superconducting gap inelastic light scattering electron-phonon interaction

Cite

@article{arxiv.cond-mat/0202134,
  title  = {Negative isotope effect of a BCS-like gap; an inelastic light scattering study},
  author = {In-Sang Yang and M. V. Klein and S. Bud'ko and P. C. Canfield},
  journal= {arXiv preprint arXiv:cond-mat/0202134},
  year   = {2007}
}

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4 pages, 4 figures

Negative isotope effect of a BCS-like gap; an inelastic light scattering study

Abstract

Keywords

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