4 research outputs found
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
Crystal structure, Fermi surface calculations and Shubnikov-de Haas oscillations spectrum of the organic metal -(BETS)HgBr(CHCl) at low temperature
The organic metal \theta_4_4_6_5$Cl) is known to
undergo a phase transition as the temperature is lowered down to about 240 K.
X-ray data obtained at 200 K indicate a corresponding modification of the
crystal structure, the symmetry of which is lowered from quadratic to
monoclinic. In addition, two different types of cation layers are observed in
the unit cell. The Fermi surface (FS), which can be regarded as a network of
compensated electron and hole orbits according to band structure calculations
at room temperature, turns to a set of two alternating linear chains of orbits
at low temperature. The field and temperature dependence of the Shubnikov-de
Haas oscillations spectrum have been studied up to 54 T. Eight frequencies are
observed which, in any case, points to a FS much more complex than predicted by
band structure calculations at room temperature, even though some of the
observed Fourier components might be ascribed to magnetic breakdown or
frequency mixing. The obtained spectrum could result from either an interaction
between the FS's linked to each of the two cation layers or to an eventual
additional phase transition in the temperature range below 200 K.Comment: accepted for publication in Solid State Science