Doubly Enhanced Skyrmions in ν = 2 Bilayer Quantum Hall States

Skyrmion excitations were measured and compared for the first time in the bilayer quantum Hall (QH) state at the Landau-level filling factor ν=2 and in the monolayer QH state at ν=1. The observed number of flipped spins, N spin , is 14 in the bilayer sample with a large tunnelling gap, and N spin =7 in the bilayer sample with a small tunnelling gap, while it is N spin =7 in the monolayer sample. The difference is interpreted to be due to the interlayer exchange interaction.