Viscoelasticity and Surface Tension at the Defect-Induced First-Order Melting Transition of a Vortex Lattice

We show that thermally activated interstitial and vacancy defects can lead to first order melting of a vortex lattice. We obtain good agreement with experimentally measured melting curve, latent heat, and magnetization jumps for YBCO and BSCCO. The shear modulus of the vortex liquid is frequency dependent and crosses over from zero at low frequencies to a finite value at high frequencies. We also find a small surface tension between the vortex line liquid and the vortex lattice.