214 research outputs found
Shubnikov-de Haas oscillations spectrum of the strongly correlated quasi-2D organic metal (ET)8[Hg4Cl12(C6H5Br)]2 under pressure
Pressure dependence of the Shubnikov-de Haas (SdH) oscillations spectra of
the quasi-two di- mensional organic metal (ET)8[Hg4Cl12(C6H5Br)]2 have been
studied up to 1.1 GPa in pulsed magnetic fields of up to 54 T. According to
band structure calculations, its Fermi surface can be regarded as a network of
compensated orbits. The SdH spectra exhibit many Fourier components typical of
such a network, most of them being forbidden in the framework of the
semiclassical model. Their amplitude remains large in all the pressure range
studied which likely rules out chemical potential oscillation as a dominant
contribution to their origin, in agreement with recent calculations relevant to
compensated Fermi liquids. In addition to a strong decrease of the magnetic
breakdown field and effective masses, the latter being likely due to a
reduction of the strength of electron correlations, a sizeable increase of the
scattering rate is observed as the applied pressure increases. This latter
point, which is at variance with data of most charge transfer salts is
discussed in connection with pressure-induced features of the temperature
dependence of the zero-field interlayer resistanceComment: Eur. Phys. J. B, in pres
Onsager phase factor of quantum oscillations in the organic metal theta-(BEDT-TTF)4CoBr4(C6H4Cl2)
De Haas-van Alphen oscillations are studied for Fermi surfaces illustrating
the Pippard's model, commonly observed in multiband organic metals. Field- and
temperature-dependent amplitude of the various Fourier components, linked to
frequency combinations arising from magnetic breakdown between different bands,
are considered. Emphasis is put on the Onsager phase factor of these
components. It is demonstrated that, in addition to the usual Maslov index,
field-dependent phase factors must be considered to precisely account for the
data at high magnetic field. We present compelling evidence of the existence of
such contributions for the organic metal theta-(BEDT-TTF)4CoBr4(C6H4Cl2)
Field-induced carrier delocalization in the strain-induced Mott insulating state of an organic superconductor
We report the influence of the field effect on the dc resistance and Hall
coefficient in the strain-induced Mott insulating state of an organic
superconductor -(BEDT-TTF)Cu[N(CN)]Br. Conductivity obeys
the formula for activated transport , where is a constant and depends on
the gate voltage. The gate voltage dependence of the Hall coefficient shows
that, unlike in conventional FETs, the effective mobility of dense hole
carriers ( cm) is enhanced by a positive gate
voltage. This implies that carrier doping involves delocalization of intrinsic
carriers that were initially localized due to electron correlation.Comment: 5 pages, 3 figure
Magnetic oscillations in a two-dimensional network of compensated electron and hole orbits
The FS of (ET)8Hg4Cl12(C6H5Br)2 can be regarded as a 2D network of
compensated electron and hole orbits coupled by magnetic breakthrough.
Simultaneous measurements of the interlayer magnetoresistance and magnetic
torque have been performed up to 28 T. Magnetoresistance and de dHvA
oscillations spectra exhibit frequency combinations typical of such a network.
Even though some of the observed magnetoresistance oscillations cannot be
interpreted on the basis of neither conventional SdH oscillations nor quantum
interference, the temperature and magnetic field (both orientation and
magnitude) dependence of all the Fourier components of the dHvA spectra can be
consistently accounted for by the LK formula. This behaviour is at variance
with that currently reported for compounds illustrating the linear chain of
coupled orbits model.Comment: accepted for publication in europhysics Letter
Temperature- and pressure-dependent metallic states in (BEDT-TTF)8[Hg4Br12(C6H5Br)2]
Temperature-driven metal-insulator and pressure-driven insulator-metal
transitions observed in(BEDT-TTF)8[Hg4X12(C6H5Y)2]] with X = Y = Br are studied
through band structure calculations based on X-ray crystal structure
determination and Shubnikov-de Haas (SdH) oscillations spectra, respectively.
In connection with chemical pressure effect, the transition, which is not
observed for X = Cl, is due to gap opening linked to structural changes as the
temperature decreases. Even though many body interactions can be inferred from
the pressure dependence of the SdH oscillations spectra, all the data can be
described within a Fermi liquid picture
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