# Probing inter- and intrachain Zhang-Rice excitons in $Li_2CuO_2$ and determining their binding energy

Monney, Claude; Bisogni, Valentina; Zhou, Ke-Jin; Kraus, Roberto; Strocov, Vladimir N; Behr, Günter; Drechsler, Stefan-Ludwig; Rosner, Helge; Johnston, Steve; Geck, Jochen; Schmitt, Thorsten (2016). Probing inter- and intrachain Zhang-Rice excitons in $Li_2CuO_2$ and determining their binding energy. Physical Review B, 94(16):Epub ahead of print.

## Abstract

Cuprate materials, such as those hosting high-temperature superconductivity, represent a famous class of materials where the correlations between the strongly entangled charges and spins produce complex phase diagrams. Several years ago, the Zhang-Rice singlet was proposed as a natural quasiparticle in hole-doped cuprates. The occurrence and binding energy of this quasiparticle, consisting of a pair of bound holes with antiparallel spins on the same $CuO_4$ plaquette, depends on the local electronic interactions, which are fundamental quantities for understanding the physics of the cuprates. Here, we employ state-of-the-art resonant inelastic x-ray scattering (RIXS) to probe the correlated physics of the $CuO_4$ plaquettes in the quasi-one-dimensional chain cuprate $Li_2CuO_2$. By tuning the incoming photon energy to the O K edge, we populate bound states related to the Zhang-Rice quasiparticles in the RIXS process. Both intra- and interchain Zhang-Rice singlets are observed and their occurrence is shown to depend on the nearest-neighbor spin-spin correlations, which are readily probed in this experiment. We also extract the binding energy of the Zhang-Rice singlet and identify the Zhang-Rice triplet excitation in the RIXS spectra.

## Abstract

Cuprate materials, such as those hosting high-temperature superconductivity, represent a famous class of materials where the correlations between the strongly entangled charges and spins produce complex phase diagrams. Several years ago, the Zhang-Rice singlet was proposed as a natural quasiparticle in hole-doped cuprates. The occurrence and binding energy of this quasiparticle, consisting of a pair of bound holes with antiparallel spins on the same $CuO_4$ plaquette, depends on the local electronic interactions, which are fundamental quantities for understanding the physics of the cuprates. Here, we employ state-of-the-art resonant inelastic x-ray scattering (RIXS) to probe the correlated physics of the $CuO_4$ plaquettes in the quasi-one-dimensional chain cuprate $Li_2CuO_2$. By tuning the incoming photon energy to the O K edge, we populate bound states related to the Zhang-Rice quasiparticles in the RIXS process. Both intra- and interchain Zhang-Rice singlets are observed and their occurrence is shown to depend on the nearest-neighbor spin-spin correlations, which are readily probed in this experiment. We also extract the binding energy of the Zhang-Rice singlet and identify the Zhang-Rice triplet excitation in the RIXS spectra.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics English 2016 11 Jan 2017 17:57 22 Feb 2017 02:03 American Physical Society 2469-9950 https://doi.org/10.1103/PhysRevB.94.165118

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