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Photogeneration of self-localized polarons in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub>and La<sub>2</sub>CuO<sub>4</sub>

Y H KimDepartment of Physics, Institute for Polymers and Organic Solids, University of California, Santa Barbara, Santa Barbara, CA 93106, USAChristopher FosterDepartment of Physics, Institute for Polymers and Organic Solids, University of California, Santa Barbara, Santa Barbara, CA 93106, USAA. J. HeegerDepartment of Physics, Institute for Polymers and Organic Solids, University of California, Santa Barbara, Santa Barbara, CA 93106, USAS. D. CoxDepartment of Chemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USAL. AcedoDepartment of Chemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USAGalen D. StuckyDepartment of Chemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
1989en
ABI

Abstract

Photoinduced infrared absorption measurements of YBa2Cu3O7-δ (δ = 0.75) and La2CuO4 are reported. We have observed photoinduced infrared active vibrational modes and associated phonon bleachings which indicate the formation of a localized structural distortion in the Cu-O plane around the photogenerated carriers. In both materials, an associated electronic transition indicates that this structural distortion causes the formation of a self-localized electronic state in the energy gap. The photoinduced distortion and the associated self-localized gap state demonstrate that the photoexcitations are relatively long-lived polarons (or bipolarons). The dynamic mass associated with the distortion is smaller in YBa2Cu3O7-δ than in La2CuO4 (smaller dynamic mass implies a longer range distortion). Since these features are not observed in the isostructural compound, La2NiO4, we conclude that polaron (or bipolaron) formation plays an important role in the high temperature superconductivity.

Identifiers

DOI
10.1088/0031-8949/1989/t27/003

Citations and references

Cited by 30 references
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