We study dynamic melting of confined vortex matter moving in disordered, mesoscopic channels by mode-locking experiments. The dynamic melting transition, characterized by a collapse of the mode-locking effect, strongly depends on the frequency, i.e., on the average velocity of the vortices. The associated dynamic ordering velocity diverges upon approaching the equilibrium melting line $T_{m,e}(B)$ as $v_c\sim (T_{m,e}-T{)}^{-1}$. The data provide the first direct evidence for velocity dependent melting and show that the phenomenon also takes place in a system under disordered confinement.

• Received 10 February 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.177002