Absence of a boron isotope effect in the magnetic penetration depth of MgB${}_2$

Abstract

The magnetic penetration depth $\lambda (0)$ in polycrystalline MgB${}_2$ for different boron isotopes (${}^{10}$B/${}^{11}$B) was investigated by transverse field muon spin rotation. No boron isotope effect on the penetration depth $\lambda (0)$ was found within experimental error: $\Delta \lambda (0)/\lambda (0)=-0.8(8)$, suggesting that MgB${}_2$ is an adiabatic superconductor. This is in contrast to the substantial oxygen isotope effect on $\lambda (0)$ observed in cuprate high-temperature superconductors.

5 pages, 3 figures, 1 table