MPI für Festkörperforschung / FKF Publikationen 2004 |
|Influence of electronic correlations and band-filling on the charge-ordering effects in two-dimensional organic conductors investigated by infrared spectroscopy|
|Authors:||Dressel, M.; Drichko, N.; Schlueter, J.; Bogdanova, O.; Zhilyaeva, E.; Lyubovskaya, R.; Greco, A.; Merino, J.|
|Date of Publication (YYYY-MM-DD):||2004|
|Title of Journal:||Journal de Physique IV|
|Review Status:||not specified|
|Abstract / Description:||A comparative study of the low-energy optical properties of the
1/4-filled two-dimensional organic conductors
alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M = K, NH4) and the 1/5-filled salt
beta"-(BEDO-TTF)(5)[CsHg(SCN)(4)](2) is presented. The superconducting
alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4) exhibits metallic-like optical
properties down to 4 K. This is in contrast to the non-superconducting
salt alpha-(BEDT-TTF)(2)KHg(SCN)(4) where a strong feature appears at
frequencies of about 200 cm(-1) and temperatures below 200 K which
indicates the opening of a pseudogap. In the anisotropic and poor metal
beta"-(BEDO-TTF)(5)[CsHg(SCN)(4)]) We find a similar pseudogap in the
optical spectra around 300 cm(-1) up to room temperature and the
presence of a strong Drude-like contribution. Based on exact
diagonalisation calculations of the optical conductivity on an extended
Hubbard model at quarter-filling we argue that the proximity of the
alpha-phase BEDT-TTF salts to a charge-ordering transition is
responsible for the observed pseudogap. Our proposed scenario suggests
that the different ground states, including superconductivity, are a
consequence of the fluctuations associated with short-range charge
ordering which builds up close to the quantum phase transition. In a
1/5-filled system similar features like the short-range checkerboard
charge fluctuations are expected, but the Drude contribution is always
present because the charge ordered state is strongly modified by the
presence of mobile empty sites.
|Free Keywords:||optical properties; charge ordering; electronic correlations;
two-dimensional organic conductors
|External Publication Status:||published|
|Communicated by:||Michaela Asen-Palmer|
|Affiliations:||MPI für Festkörperforschung|
|External Affiliations:||Univ Stuttgart, Inst Phys, D-70550 Stuttgart, Germany.
; AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia.
; Argonne Natl Lab, Div Mat Sci, Argonne, IL 60439 USA.
; Russian Acad Sci, Inst Problems Chem Phys, Chernogolovka 142432, Russia.
; Fac Ciencias Exactas Ingn & Agrimensura, Rosario, Argentina.
; Inst Fis Rosario, Rosario, Argentina.
; Max Planck Inst Festkorperforsch, D-70506 Stuttgart, Germany.
|Identifiers:||ISI:000221218200043 [ID No:1] |
ISSN:1155-4339 [ID No:2]
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