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 nu. The stability of various QH states are examined by varying the density balance between the two layers. We observe a remarkable nu-dependent behavior; the interlayer charge transfer is allowed for particular values of nu, 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. (C) 1999 Elsevier Science Ltd. All rights reserved.