### Session Q22: Metal-Insulator Phase Transitions II

11:15 AM–2:15 PM, Wednesday, March 23, 2011
Room: D163

Chair: Cengiz Sen, University of Tennessee

Abstract ID: BAPS.2011.MAR.Q22.11

### Abstract: Q22.00011 : Localized states in Mott insulator $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_{2}$]Cl probed by photoluminescence

1:15 PM–1:27 PM

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#### Authors:

Natalia Drichko
(Johns Hopkins University)

Rudi Hackl
(Walter Meissner Institute Garching Germany)

John Schlueter
(Argonne National Laboratory)

We present the luminescence spectra of a low-temperature Mott insulator (T$_c$=35 K) $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_{2}$]Cl and a metal with a superconductor transition $\kappa$-(BE\-DT\--TTF)$_2$\-Cu\-[N\-(CN)$_{2}$]Br in the temperature range between 300 and 10 K. In the Mott insulating state we observe an appearance of a luminescence at 1.95 eV, which corresponds to a LUMO-HOMO transition in a BEDT-TTF molecule. This luminescence is quenched both in the higher-temperature semiconducting state of $\kappa$-(BE\-DT\--TTF)$_2$\-Cu\-[N\-(CN)$_{2}$]Cl and metallic $\kappa$-(BE\-DT\--TTF)$_2$\-Cu\-[N\-(CN)$_{2}$]Br. To our knowledge, it is the first observation of luminescence driven by electronic correlations. This observation gives an evidence of the local character of BEDT-TTF energy levels in the Mott insulating state, in contrast to the band-character in the metallic and semiconducting states.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.Q22.11