Upper Limit of the Bose-Glass Transition inYBa2Cu3O7at High Density of Columnar Defects

The Bose-glass transition in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$ single crystals with columnar defects produced by irradiation with 5.8 GeV Pb ions was studied both experimentally and theoretically. The Bose-glass transition line $B_{\mathrm{BG}}\left(T\right)$ progressively shifts upwards with increasing doses of irradiation $\phi$, up to ${10}^{11}\mathrm{ions}/{\mathrm{cm}}^2$. For larger $\phi$, the $B_{\mathrm{BG}}\left(T\right)$ line does not shift anymore, and saturates at $B_{\mathrm{BG}}^{\max }\left(T\right)$, which is still considerably below $H_{c2\mathrm{}}\left(T\right)$. Theoretically, we show that the observed evolution of the Bose-glass transition line provides strong evidence for an intermediate or disentangled vortex liquid phase, sandwiched between the melting line $B_m\left(T\right)$ and $B_{\mathrm{BG}}^{\max }\left(T\right)$, in virgin samples.