Interlayer charge transfer in bilayer quantum Hall states at various filling factors

We have studied bilayer quantum Hall (QH) effects in double-quantum-well structures at various Landau-level (LL) filling factors v. The stability of various QH states are examined by varying the density balance between the two layers. We observe a remarkable v-dependent behavior; the interlayer charge transfer is allowed for particular values of v, which then repeat in a characteristic sequence with a period of 4. We employ a pseudospin picture, by which the interlayer charge transfer is expressed as a rotation of the total pseudospin. The ability or inability to accommodate the charge transfer represents the degree of pseudospin polarization in the bilayer QH state.