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Nature of optical excitations in the frustrated kagome compound herbertsmithite

A. Pustogow, Y. Li, I. Voloshenko, P. Puphal, C. Krellner, I. I. Mazin, M. Dressel, and R. Valentí
Phys. Rev. B 96, 241114(R) – Published 29 December 2017
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Abstract

Optical conductivity measurements are combined with density functional theory calculations in order to understand the electrodynamic response of the frustrated Mott insulators herbertsmithite ZnCu3(OH)6Cl2 and the closely related kagome-lattice compound Y3Cu9(OH)19Cl8. We identify these materials as charge-transfer rather than Mott-Hubbard insulators, similar to the high-Tc cuprate parent compounds. The band edge is at 3.3 and 3.6 eV, respectively, establishing the insulating nature of these compounds. Inside the gap, we observe dipole-forbidden local electronic transitions between the Cu 3d orbitals in the range 1–2 eV. With the help of ab initio calculations we demonstrate that the electrodynamic response in these systems is directly related to the role of on-site Coulomb repulsion: While charge-transfer processes have their origin on transitions between the ligand band and the Cu 3d upper Hubbard band, local dd excitations remain rather unaffected by correlations.

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  • Received 18 September 2017

DOI:https://doi.org/10.1103/PhysRevB.96.241114

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

A. Pustogow1,*, Y. Li2, I. Voloshenko1, P. Puphal3, C. Krellner3, I. I. Mazin4, M. Dressel1, and R. Valentí2

  • 11. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
  • 2Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
  • 3Physikalisches Institut, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
  • 4Code 6393, Naval Research Laboratory, Washington, D.C. 20375, USA

  • *Corresponding author: andrej.pustogow@pi1.physik.uni-stuttgart.de

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Issue

Vol. 96, Iss. 24 — 15 December 2017

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