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Abstract:
The isotope coefficient beta of the magnetic penetration depth in the superconducting state is studied at T = 0 for a d-CDW and a nodal metal model. Disregarding superconductivity the Fermi surface of the first model possesses arcs whereas the second model has no arcs. We show that a large increase of beta in the pseudogap region is generically incompatible with Fermi arcs in the pseudogap state. Thus only the second model shows a large increase of beta with decreasing doping. The required electron-phonon coupling is small and compatible with first-principles calculations based on the local density approximation (LDA). Copyright (C) EPLA, 2011
