Comparative study of theI−Vscaling in highly anisotropicBi2Sr2CaCu2O8+δand isotropic(K,Ba)BiO3heavy-ion-irradiated single crystals

Abstract

The Bose-glass transition has been investigated by transport measurements on heavy-ion irradiated ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ and isotropic $(\mathrm{K},\mathrm{B}\mathrm{a}){\mathrm{BiO}}_{3}$ single crystals. When a magnetic field was applied parallel to the defects, we show that, for ${B}_{\ensuremath{\varphi}}/10l{\ensuremath{\mu}}_{0}Hl{B}_{\ensuremath{\varphi}},$ the same scaling functions could be used to describe the transition in these two systems emphasizing the universality of this transition. The field and sample-independent critical exponents which were found to be ${\mathbf{\ensuremath{\nu}}}_{\ensuremath{\perp}}=1.1\ifmmode\pm\else\textpm\fi{}0.1,$ $z=5.3\ifmmode\pm\else\textpm\fi{}0.2,$ and $\ensuremath{\alpha}(\ensuremath{\equiv}{\ensuremath{\nu}}_{\ensuremath{\parallel}}/{\mathbf{\ensuremath{\nu}}}_{\ensuremath{\perp}})=2,$ are consistent with Monte Carlo simulations with screened vortex interactions and columnar defects. In addition, we found that in both systems, the creep process in the Bose glass phase could be described by the variable-range hopping mechanism of flux lines with the glassy exponent value of $\ensuremath{\mu}=1/3$ which is close to the transition and the creep exponent $\ensuremath{\mu}\ensuremath{\approx}1$ at lower temperatures suggests that creep is then dominated by a generation of half loops expanding along the track direction.