Transport measurements using the dc flux transformer configuration together with $c$-axis resistance data in clean and twinned $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ single crystals show that vortices are localized by the twin-boundary potential. The results support the existence of a divergent tilt modulus [D. R. Nelson and V. M. Vinokur, Phys. Rev. B 48, 13 060 (1993)] in a liquid that freezes into a Bose glass.

• Received 18 December 1995

DOI:https://doi.org/10.1103/PhysRevB.53.R8895