Resonantly enhanced tunneling in a double layer quantum Hall ferromagnet

The tunneling conductance between two parallel 2D electron systems has been measured in a regime of strong interlayer Coulomb correlations. At total L andau level filling nu(tau) = 1 the tunnel spectrum changes qualitatively w hen the boundary separating the compressible phase from the ferromagnetic q uantized Hall state is crossed. A huge resonant enhancement replaces the st rongly suppressed equilibrium tunneling characteristic of weakly coupled la yers. The possible relationship of this enhancement to the Goldstone mode o f the broken symmetry ground state is discussed.