Preferred number of flipped spins in Skyrmion excitation

Abstract We measured the activation energy of the Skyrmion excitations in the monolayer quantum Hall (QH) state at the Landau-level filling factor ν =1 and in the bilayer QH state at ν =2. The number of flipped spins N s changes from 7 to 1 in the monolayer sample and in the bilayer sample with small tunneling energy gap, while N s changes from 14 to 7 and finally to 1 in the bilayer sample with large tunneling energy gap. These experimental data suggest the existence of the preferred number of flipped spins N s =7 for a Skyrmion-pair excitation.