Nature of optical excitations in the frustrated kagome compound Herbertsmithite

Abstract

Optical conductivity measurements are combined with density functional theory calculations in order to understand the electrodynamic response of the frustrated Mott insulators Herbertsmithite $\mathrm{ZnC}{\mathrm{u}}_3(\mathrm{OH}{)}_6\mathrm{C}{\mathrm{l}}_2$ and the closely-related kagome-lattice compound ${\mathrm{Y}}_3\mathrm{C}{\mathrm{u}}_9(\mathrm{OH}{)}_{19}\mathrm{C}{\mathrm{l}}_8$. We identify these materials as charge-transfer rather than Mott-Hubbard insulators, similar to the high-$T_c$ 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 \textit{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, \textit{local} $d$-$d$ excitations remain rather unaffected by correlations.

arXiv comment5 pages, 5 figures, Supplemental Material

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Cited by in corpus (12)

• Quantum Spin Liquids Unveil the Genuine Mott State
• From Claringbullite to a new spin liquid candidate Cu${}_3$Zn(OH)${}_6$FCl
• Local study of the insulating quantum kagome antiferromagnets YCu3(OH)6OxCl3-x (x=0,1/3)
• Electrodynamics of quantum spin liquids
• Controlling frustrated magnetism on the kagome lattice by uniaxial-strain tuning
• Lattice dynamics in the spin-1/2 frustrated kagome compound herbertsmithite
• Magnetization Plateau Observed by Ultra-High Field Faraday Rotation in a Kagomé Antiferromagnet Herbertsmithite
• Low-Energy Excitations in Quantum Spin-Liquids Identified by Optical Spectroscopy
• $LnC{u}_3(OH{)}_{6}C{l}_3(Ln=Gd,Tb,Dy)$: Heavy Lanthanides on Spin-1/2 Kagome Magnets
• Thermodynamic, dynamic and transport properties of quantum spin liquid in herbertsmithite from experimental and theoretical point of view
• Six magnetization plateau phases in a spin-1/2 distorted kagome antiferromagnet: application to ${\mathrm{Y}}_3{\mathrm{Cu}}_9(\mathrm{OH}{)}_{19}{\mathrm{Cl}}_8$
• Lattice dynamics of the frustrated kagome compound Y-kapellasite