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Mid-infrared absorption in YBa2Cu3O6: Failure of spin-wave theory in undoped cuprates?

M. Grueninger·D. van der Marel·A. Damascelli·A. Erb·Th. Wolf·T. Nunner·T. Kopp
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Abstract

The optical conductivity sigma (omega) of undoped YBa2Cu3O6 is studied in detail in the mid-infrared range. Substitutions on all but the Ba site are used to identify the prominent absorption processes at 2800 and 3800 cm^-1. Experimental evidence for bimagnon-plus-phonon absorption is collected. A more critical analysis of the lineshape and the spectral weight reveals the limits of this approach. Although phonon-2-magnon multiple scattering seems to reproduce the lineshape, the necessary coupling is unrealistically large. The strong increase of high frequency spectral weight with increasing temperature makes the failure of spin-wave theory even more evident.

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M. Grueninger, D. van der Marel, A. Damascelli, A. Erb, Th. Wolf, T. Nunner, T. Kopp. 1999-04-27. Mid-infrared absorption in YBa2Cu3O6: Failure of spin-wave theory in undoped cuprates?. https://doi.org/10.1103/physrevb.62.12422

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