Electronic correlation in the infrared optical properties of the quasi two dimensional $κ$-type BEDT-TTF dimer system

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dc.creatorSasaki, T.
dc.creatorIto, I.
dc.creatorYoneyama, N.
dc.creatorKobayashi, N.
dc.creatorHanasaki, N.
dc.creatorTajima, H.
dc.creatorIto, T.
dc.creatorIwasa, Y.
dc.date2003-08-26
dc.date.accessioned2026-07-07T02:53:07Z
dc.date.available2026-07-07T02:53:07Z
dc.descriptionThe polarized optical reflectance spectra of the quasi two dimensional organic correlated electron system $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]$Y$, $Y =$ Br and Cl are measured in the infrared region. The former shows the superconductivity at $T_{\rm c} \simeq$ 11.6 K and the latter does the antiferromagnetic insulator transition at $T_{\rm N} \simeq$ 28 K. Both the specific molecular vibration mode $ν_{3}(a_{g})$ of the BEDT-TTF molecule and the optical conductivity hump in the mid-infrared region change correlatively at $T^{*} \simeq$ 38 K of $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, although no indication of $T^{*}$ but the insulating behaviour below $T_{\rm ins} \simeq$ 50-60 K are found in $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl. The results suggest that the electron-molecular vibration coupling on the $ν_{3}(a_{g})$ mode becomes weak due to the enhancement of the itinerant nature of the carriers on the dimer of the BEDT-TTF molecules below $T^{*}$, while it does strong below $T_{\rm ins}$ because of the localized carriers on the dimer. These changes are in agreement with the reduction and the enhancement of the mid-infrared conductivity hump below $T^{*}$ and $T_{\rm ins}$, respectively, which originates from the transitions between the upper and lower Mott-Hubbard bands. The present observations demonstrate that two different metallic states of $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br are regarded as {\it a correlated good metal} below $T^{*}$ including the superconducting state and {\it a half filling bad metal} above $T^{*}$. In contrast the insulating state of $κ$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Cl below $T_{\rm ins}$ is the Mott insulator.
dc.description8 pages, 7 figures
dc.identifierhttps://arxiv.org/abs/cond-mat/0308520
dc.identifierhttp://arxiv.org/abs/cond-mat/0308520
dc.identifierPhys. Rev. B 69, 064508 (2004)
dc.identifierdoi:10.1103/PhysRevB.69.064508
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/22087
dc.subjectSuperconductivity
dc.subjectStrongly Correlated Electrons
dc.titleElectronic correlation in the infrared optical properties of the quasi two dimensional $κ$-type BEDT-TTF dimer system
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