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arXiv · 1309.3670

Localized states in the Mott insulator κ-(BEDT-TTF)_2Cu[N(CN)_2]Cl as probed by photoluminescence

N. Drichko·R. Hackl·J. A. Schlueter
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Abstract

We compare the photoluminescence spectra of the low-temperature Mott insulator \etcl (T_{MIT}=40 K) with spectra of metallic κ-(BEDT-TTF)_2Cu[N(CN)_2]Br, which is superconducting below T_c=11.8 K, in the temperature range between 300 and 20 K. In the Mott insulating state of κ-(BEDT-TTF)_2Cu[N(CN)_2]Cl we observe a luminescence band at 1.95 eV due to the recombination of an exciton created by a HOMO-LUMO optical excitation. This luminescence is quenched both in the high-temperature bad metal state of κ-(BEDT-TTF)_2Cu[N(CN)_2]Cl and in metallic κ-(BEDT-TTF)_2Cu[N(CN)_2]Br. The observation of the luminescence of an exciton provides evidence for the local character of excitations in the Mott insulating state.

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N. Drichko, R. Hackl, J. A. Schlueter. 2013-09-14. Localized states in the Mott insulator κ-(BEDT-TTF)_2Cu[N(CN)_2]Cl as probed by photoluminescence. https://doi.org/10.1103/physrevb.88.115109

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