Optical studies of gap, exchange, and hopping energies in the insulating cuprates

S. L. Cooper, G. A. Thomas, A. J. Millis, P. E. Sulewski, J. Orenstein, D. H. Rapkine, S. W. Cheong, P. L. Trevor

Research output: Contribution to journalArticlepeer-review


We have measured the insulating energy gap and the exchange interaction J in a series of cuprate crystals, including T-phase M2CuO4 (M=Pr, Nd, Sm, Eu, and Gd), T*-phase La,Tb,Sr2CuO4, and T-phase La2CuO4. We find that the energy gap scales predominantly with the in-plane Cu-O distance, scaling as loglogd-6. Furthermore, contrary to simple expectations, the energy gap increases with decreasing Cu-O distance, suggesting that Coulomb and other repulsive energies dominate the effects of band hybridization. Using a three-band Hubbard-model expression, our studies of and J in the cuprates allow us to estimate that the hopping energy t scales with Cu-O distance as logt/ logd-4.

Original languageEnglish (US)
Pages (from-to)10785-10788
Number of pages4
JournalPhysical Review B
Issue number16
StatePublished - 1990
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics


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