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

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