arXiv subjects
Publications and source records attributed to H. Luetkens.
We have used the technique of low energy muon spin rotation to measure the local magnetic field profile B(z) beneath the surface of a lead film maintained in the Meissner state (z depth from the surface, z <= 200 nm). The data unambiguously show that B(z) clearly deviates from an exponential law and represent the first direct, model independent proof for a non-local response in a superconductor.
We report the first direct observation of the oxygen-isotope ($^{16}$O/$^{18}$O) effect on the in-plane penetration depth $λ_{ab}$ in a nearly optimally doped YBa$_2$Cu$_3$O$_{7-δ}$ film using the novel low-energy muon-spin rotation technique. Spin polarized low energy muons are implanted in the film at a known depth $z$ beneath the surface and precess in the local magnetic field $B(z)$. This feature allows us to measure directly the profile $B(z)$ of the magnetic field inside the superconducting film in the Meissner state and to make a model independent determination of $λ_{ab}$. A substantial isotope shift $Δλ_{ab}/λ_{ab}=2.8(7)$% at 4 K is observed, implying that the in-plane effective supercarrier mass $m_{ab}^\ast$ is oxygen-isotope dependent with $Δm_{ab}^\ast/m_{ab}^\ast = 5.5(1.4)%$.