title: Collapse of coherent quasiparticle states in theta-(BEDT-TTF)2I3 observed by optical spectroscopy.
abstract: Optical conductivity measurements on the organic metal theta-(BEDT-TTF)2I3 revealed that the system crosses over rapidly from a coherent quasiparticle state to an incoherent state with temperature. Despite the metallic temperature dependence of resistivity, a well-defined Drude peak at low temperatures turns into a far-infrared peak with temperature. The peak energy shifts to higher frequencies and, simultaneously, the spectral weight is transferred to high frequencies beyond the electron band width. These characteristics imply that theta-(BEDT-TTF)2I3, so far believed to be a typical metal, is in fact a strongly correlated electron system with "bad-metal" character.
authors.affiliation: RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan. k-takenaka@postman.riken.jp
authors.forename: K
authors.initials: K
authors.lastname: Takenaka
authors.forename: M
authors.initials: M
authors.lastname: Tamura
authors.forename: N
authors.initials: N
authors.lastname: Tajima
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: J
authors.initials: J
authors.lastname: Nohara
authors.forename: S
authors.initials: S
authors.lastname: Sugai
mesh_terms: D004553:Electric Conductivity; D055095:Optics and Photonics; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D013057:Spectrum Analysis / Q000379:methods*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: C472948:BEDT-TTF; D009942:Organometallic Compounds; D011522:Protons; D013438:Sulfhydryl Compounds