Preferred number of flipped spins in Skyrmion excitation

We measured the activation energy of the Skyrmion excitations in the monola yer quantum Hall (QH) state at the Landau-level filling factor v = 1 and in the bilayer QH state at v = 2. The number of flipped spins N-s changes fro m 7 to 1 in the monolayer sample and in the bilayer sample with small tunne ling energy gap, while N-s changes from 14 to 7 and finally to 1 in the bil ayer sample with large tunneling energy gap. These experimental data sugges t the existence of the preferred number of flipped spins N-s = 7 for a Skyr mion-pair excitation. (C) 2001 Elsevier Science B.V. All rights reserved.