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Anomalous optical properties of the mixed-valent lithium cuprate LiCu2O2

R. V. Pisarev, A. S. Moskvin, A. M. Kalashnikova, A. A. Bush, Th. Rasing

DOI 10.1103/PhysRevB.74.132509 · Physical Review B

T1

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Abstract

We show that the optical properties of LiCu1+Cu2+O2 in the spectral range of 0.6–5.8eV radically differ from those of all other known Cu1+, Cu2+, and mixed-valent oxide cuprates. An extremely strong, sharp, and highly anisotropic optical feature with ε2xx=26 is observed at 3.27eV which we assign to an excitonlike transition in the O2−−Cu1+−O2− dumbbells. Our findings thoroughly disagree with reported ab initio calculations and can be explained by an exciton-type model that includes strong electron-hole correlations and a crystal-field splitting of the Cu1+ states. The excitonic effects in LiCu2O2 appear strongly enhanced due to the shortening of the dumbbell lattice spacing which is the shortest one among known cuprates. Our experimental data along with the model reveal a previously unknown regularity in the electronic structure of cuprates.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
YBa2Cu3O6

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—Pressure not reportedunknown

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