Bose-glass and entanglement - Disentanglement transitions in YBa₂Cu₃O₇

The Bose-glass transition field BBG in YBa2Cu3O7 single crystals with columnar defects is tracked by the onset of the third harmonic generation. The progressive upward shift of the BBG(T)-line with the irradiation dose is followed by a saturation for the matching fields BΦ=20 kG - 100 kG. The uppermost position of the Bose-glass transition is interpreted as a boundary between entangled and disentangled vortex liquids in virgin YBa2Cu3O7.