Stable circulation in superfluid³He-A

We present evidence of stable nonzero circulation in superfluid³He-A around a 16 μm diameter wire. The measurements are made on a rotating cryostat at T≈0.15T_c. Circulation offects the splitting of the wire's normal modes, which changes the beat frequency in the emf across the wire as it vibrates in a magnetic field. The different beat frequencies at 14 and at 21 bar suggest that circulation is present at 21 bar. Furthermore, at 21 bar the beat frequency is a linear function of rotation velocity, as is expected if circulation is trapped around the wire. At 14 bar no effect of rotation is observed. We propose that at 21 bar the ground state texture has nonzero circulation of order h/2m₃.