Stripes in Double Layer Quantum Hall Systems

We present results of a study of double layer quantum Hall systems in which each layer has a high-index Landau level that is half-filled. Hartree-Fock calculations indicate that, above a critical layer separation, the system becomes unstable to the formation of a unidirectional coherent charge density wave (UCCDW), which is related to stripe states in single layer systems(L. Brey and H.A. Fertig, Phys. Rev. B 62, 10268 (2000)). The UCCDW state supports low-energy modes associated with interlayer coherence, which for large enough separation and small tunneling amplitude have a line of nearly vanishing energy in the Brillouin zone. The system supports charged soliton excitations ; these become gapless in the limit of vanishing tunneling which should lead to power-law (i.e., critical) behavior in various correlation functions.