Possible Bragg-Bose glass phase in vortex states of high-Tc superconductors with sparse and weak columnar defects

The phase diagram of vortex states in the plane of density of columnar defects v8. temperature is obtained by large-scale Monte Carlo simulations of the three-dimensional anisotropic, frustrated XY model. At low temperatures and low densities of columnar defects, a phase characterized by hexagonal Bragg peaks and the diverging tilt modulus is observed, which may be the Bragg-Bose glass phase. As the temperature increases, the first-order melting transition to the interstitial liquid takes place. This melting temperature increases along with the density of columnar defects owing to "selected pinning" of flux lines. When the density of defects further increases, the transition to the Bose glass phase occurs.