Rotationally induced dissipation peak and dynamics of 3D vortex lines

Vortex dynamics of superfluid He-4 films in porous glass has been investiga ted with torsional oscillator technique under rotation. In addition to the 2D vortex dissipation peak, a new dissipation peak near the superfluid phas e transition is found. Its dependence on the rotation velocity as well as o n the temperature is studied. The rotation speed dependence of the Q value at the new peak traces no hysteresis through one rotation sweep cycle. This is argued as a mobility of 3D vortex lines which increases with increasing temperature. The temperature dependence of the mobility could be interpret ed as melting of the vortex solid, (C) 2000 Elsevier Science B.V. All right s reserved.