Europhys. Lett.
Volume 76, Number 5, December 2006
Page(s) 891 - 897
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 10 November 2006
Europhys. Lett., 76 (5), pp. 891-897 (2006)
DOI: 10.1209/epl/i2006-10371-6

The electronic states of two oppositely doped Mott insulators bilayers

T. C. Ribeiro1, 2, A. Seidel1, 2, J. H. Han3, 4 and D.-H. Lee1, 2

1  Department of Physics, University of California at Berkeley - CA 94720-7300, USA
2  Materials Sciences Division, Lawrence Berkeley National Laboratory Berkeley, CA 94720, USA
3  Department of Physics, Sungkyunkwan University - Suwon 440-746, Korea
4  CSCMR, Seoul National University - Seoul 151-747, Korea

received 29 August 2006; accepted in final form 16 October 2006
published online 10 November 2006

We study the effect of Coulomb interaction between two oppositely doped low-dimensional tJ model systems. We exactly show that, in the one-dimensional case, an arbitrarily weak interaction leads to the formation of charge neutral electron-hole pairs. We then use two different mean-field theories to address the two-dimensional case, where inter-layer excitons also form and condense. We propose that this results in new features which have no analog in single layers, such as the emergence of an insulating spin liquid phase. Our simple bilayer model might have relevance to the physics of doped Mott insulator interfaces and of the new four layer $\chem{Ba_{2}Ca_{3}Cu_{4}O_{8}}$ compound.

71.10.-w - Theories and models of many-electron systems.
71.10.Hf - Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems.
71.35.-y - Excitons and related phenomena.

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