  We induce a quantum phase transition of the 103mRh excitation at the critical
density of 10^{12} cm^{-3} by bremsstrahlung pumping at 300 K. A massive 103mRh
spin-density wave carrying a spin current moves on the identical 103Rh matrix
like a quantum fluid. The collapse-and-revival spectral evolution indicates
that the collective nuclear excitation undergoes dynamic Bose-Einstein
condensation. Applying an external magnetic field, we observe the
Onsager-Feynman quantization, which gives further evidence of the superfluidic
phase.
