Simulation of flux lines with columnar pins: Bose glass and entangled liquids

Using path integral Monte Carlo we simulate a 3D system of up to 1000 magne tic flux lines by mapping it onto interacting bosons in (2 + 1)D. With incr easing temperatures we find first order melting from an ordered solid to an entangled liquid signaled by a finite entropy jump and sharp discontinuiti es of the defect density and the structure factor S(G). For a particular de nsity of strong columnar pins the crystal is transformed into a Bose glass phase with patches of crystalline order disrupted by the trapped vortices a t the pinning sites but with no overall positional or orientational order. This glassy phase melts into a defected entangled liquid through a continuo us transition.