35 research outputs found
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
Competing types of quantum oscillations in the 2D organic conductor (BEDT-TTF)8Hg4Cl12(C6H5Cl)2
Interlayer magnetoconductance of the quasi-two dimensional organic metal
(BEDT-TTF)8Hg4Cl12(C6H5Cl)2 has been investigated in pulsed magnetic fields
extending up to 36 T and in the temperature range from 1.6 to 15 K. A complex
oscillatory spectrum, built on linear combinations of three basic frequencies
only is observed. These basic frequencies arise from the compensated closed
hole and electron orbits and from the two orbits located in between. The field
and temperature dependencies of the amplitude of the various oscillation series
are studied within the framework of the coupled orbits model of Falicov and
Stachowiak. This analysis reveals that these series result from the
contribution of either conventional Shubnikov-de Haas effect (SdH) or quantum
interference (QI), both of them being induced by magnetic breakthrough.
Nevertheless, discrepancies between experimental and calculated parameters
indicate that these phenomena alone cannot account for all of the data. Due to
its low effective mass, one of the QI oscillation series - which corresponds to
the whole first Brillouin zone area - is clearly observed up to 13 K.Comment: 8 pages, 8 figures. To be published in Phys. Rev.
High frequency magnetic oscillations of the organic metal -(ET)ZnBr(CHCl) in pulsed magnetic field of up to 81 T
De Haas-van Alphen oscillations of the organic metal
-(ET)ZnBr(CHCl) are studied in pulsed magnetic
fields up to 81 T. The long decay time of the pulse allows determining reliable
field-dependent amplitudes of Fourier components with frequencies up to several
kiloteslas. The Fourier spectrum is in agreement with the model of a linear
chain of coupled orbits. In this model, all the observed frequencies are linear
combinations of the frequency linked to the basic orbit and to the
magnetic-breakdown orbit .Comment: 6 pages, 4 figure
Quantum oscillations in the linear chain of coupled orbits: the organic metal with two cation layers theta-(ET)(4)CoBr(4)(C(6)H(4)Cl(2))
Analytical formulae for de Haas-van Alphen (dHvA) oscillations in linear
chain of coupled two-dimensional (2D) orbits (Pippard's model) are derived
systematically taking into account the chemical potential oscillations in
magnetic field. Although corrective terms are observed, basic (alpha) and
magnetic breakdown-induced (beta and 2beta - alpha) orbits can be accounted for
by the Lifshits-Kosevich (LK) and Falicov-Stachowiak semiclassical models in
the explored field and temperature ranges. In contrast, the 'forbidden orbit'
beta - alpha amplitude is described by a non-LK equation involving a product of
two classical orbit amplitudes. Furthermore, strongly non-monotonic field and
temperature dependence may be observed for the second harmonics of basic
frequencies such as 2alpha and the magnetic breakdown orbit beta + alpha,
depending on the value of the spin damping factors. These features are in
agreement with the dHvA oscillation spectra of the strongly 2D organic metal
theta- theta-(ET)(4)CoBr(4)(C(6)H(4)Cl(2)).Comment: to be published in Europhysics Letters (2012
Optical properties of organic conductor (ET)HgI : alternative type of electron-vibrational interaction
The reflectivity spectra of single crystals of (ET)HgI and
(d-ET)HgI were studied. In contrant with earlier studied clorine- and
brominemercurate compounds of the series (ET)Hg - X (X = Cl, Br, I),
the spectra of iodinemercurate compounds exhibit low reflectivity without well-defined plasma
edge and without electron-vibrational bands in the region 1 000 - 1 400 cm. The latter
fact may be due to electron-vibrational interaction with non-totally symmetric modes which
may originate from peculiarities of crystal structure of iodinemercurate compounds. A phase
transition of the first type is observed both for (ET)HgI and
(d-ET)HgI. At the transition temperature a jump in conductivity and
reflectivity is observed
Anisotropy of Magnetoresistance and Shubnikov-de Haas Oscillations in Organic Metal (ET)CuCl • HO
Behavior of the magnetoresistance has been studied in organic quasi two-dimensional metal (ET)CuCl•HO. Shubnikov-de Haas oscillations have been observed at the magnetic field directions near H ∥ c*. The oscillations frequency at H ∥ c* equals 45 T that corresponds approximately to 1% of the first Brillouin zone cross-section. The angle dependence of the oscillations frequency allows one to imagine at least the part of Fermi surface in the form of cylinder with an axis along c*
Crossover from the weak to strong-field behavior of the longitudinal interlayer magnetoresistance in quasi-two-dimensional conductors
We investigate the monotonic growth of longitudinal interlayer
magnetoresistance , analytically and numerically in the
self-consistent Born approximation. We show that in a weak magnetic field the
monotonic part of is almost constant and starts to grow
only above the crossover field , when the Landau levels (LL) become
isolated, i.e. when the LL separation becomes greater than the LL broadening.
In higher field , in
agreement with previous works.Comment: 5 pages, 3 figure