The effect of Zn-doping on the magnetic field induced dimensional crossover in YBa₂Cu₄O₈

In YBa₂Cu₄O₈ (Y124), the c-axis resistivity ρ_c(T) shows a drastic change from metallic to insulating behavior above a crossover magnetic field B_cr (B ∥ a), namely a magnetic field induced dimensional crossover. A simple picture for quasi-1-dimensional (quasi-1D) band transport along the CuO chains, originally proposed by Gorkov and Lebed, was suggested as the mechanism for this novel phenomenon. To further test the proposed picture, similar measurements on Y124 crystals doped with Zn were performed. Zn-doping is found to alter significantly ρ_c(T) at low temperatures but has little effect on the magnetic field induced dimensional crossover. These results are in good agreement with the predictions of the quasi-1D chain model and appear to confirm the critical role of the CuO chains in metallizing the c-axis in Y124.