Stripe formation and disorder induced stripe fragmentation

We have analyzed the zero field and high field transport properties of seve ral underdoped high-T-c systems. A convincing scaling behavior of the tempe rature dependence of the resistivity has been found for all of them, thus p roving that the underlying scattering mechanism remains the same as we appr oach the metal-insulator transition from the metallic side. The scaling tem perature Delta grows substantially with the decreasing hole concentration x . We associate Delta with the opening of the spin-gap in the spin ladders a ppearing due to the stripe formation. Three distinctly different temperatur e regimes have been identified: (i) high-temperature Heisenberg-like 2D reg ime; (ii) intermediate temperature 1D stripe regime;: and (iii) low-tempera ture disorder-induced stripe fragmentation and pinning with an enhanced int er-fragment and inter-stripe hole hopping, which recovers an effective 2D w eak localization with a logarithmic behavior of resistivity with temperatur e. This third regime has been revealed by suppressing superconductivity in fields up to 60 T. Hall conductivity data are used to estimate the evolutio n of the stripe "order parameter" and mobility with temperature in the norm al state.