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Bandwidth-controlled Mott transition in $κ-(BEDT-TTF)_2 Cu [N(CN)_2] Br_x Cl_{1-x}$ I. Optical studies of localized charge excitations

Daniel Faltermeier·Jakob Barz·Michael Dumm·Natalia Drichko·Martin Dressel·Boris Petrov·Victor Semkin·Rema Vlasova·Cécile Meziere·Patrick Batail
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Abstract

Infrared reflection measurements of the half-filled two-dimensional organic conductors $κ$-(BEDT-TTF)$_2$Cu[N(CN)$_{2}$]Br$_{x}$Cl$_{1-x}$ were performed as a function of temperature ($5 {\rm K}<T<300$ K) and Br-substitution ($x=0%$, 40%, 73%, 85%, and 90%) in order to study the metal-insulator transition. We can distinguish absorption processes due to itinerant and localized charge carriers. The broad mid-infrared absorption has two contributions: transitions between the two Hubbard bands and intradimer excitations from the charges localized on the (BEDT-TTF)$_2$ dimer. Since the latter couple to intramolecular vibrations of BEDT-TTF, the analysis of both electronic and vibrational features provides a tool to disentangle these contributions and to follow their temperature and electronic-correlations dependence. Calculations based on the cluster model support our interpretation.

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Daniel Faltermeier, Jakob Barz, Michael Dumm, Natalia Drichko, Martin Dressel, Boris Petrov, Victor Semkin, Rema Vlasova, Cécile Meziere, Patrick Batail. 2007-03-13. Bandwidth-controlled Mott transition in $κ-(BEDT-TTF)_2 Cu [N(CN)_2] Br_x Cl_{1-x}$ I. Optical studies of localized charge excitations. https://doi.org/10.1103/physrevb.76.165113

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