49 research outputs found
Coherent vs incoherent interlayer transport in layered metals
The magnetic-field, temperature, and angular dependence of the interlayer
magnetoresistance of two different quasi-two-dimensional (2D) organic
superconductors is reported. For -(BEDT-TTF)I we find a
well-resolved peak in the angle-dependent magnetoresistance at (field parallel to the layers). This clear-cut proof for the coherent
nature of the interlayer transport is absent for
''-(BEDT-TTF)SFCHCFSO. This and the non-metallic
behavior of the magnetoresistance suggest an incoherent quasiparticle motion
for the latter 2D metal.Comment: 4 pages, 4 figures. Phys. Rev. B, in pres
Quantum Oscillations of Electrons and of Composite Fermions in Two Dimensions: Beyond the Luttinger Expansion
Quantum oscillation phenomena, in conventional 2-dimensional electron systems
and in the fractional quantum Hall effect, are usually treated in the
Lifshitz-Kosevich formalism. This is justified in three dimensions by
Luttinger's expansion, in the parameter . We show that in two
dimensions this expansion breaks down, and derive a new expression, exact in
the limit where rainbow graphs dominate the self-energy. Application of our
results to the fractional quantum Hall effect near half-filling shows very
strong deviations from Lifshitz-Kosevich behaviour. We expect that such
deviations will be important in any strongly-interacting 2-dimensional
electronic system.Comment: 4 pages, 3 figures, LaTe
Slow oscillations of magnetoresistance in quasi-two-dimensional metals
Slow oscillations of the interlayer magnetoresistance observed in the layered
organic metal -(BEDT-TTF)IBr are shown to originate from the
slight warping of its Fermi surface rather than from independent small
cyclotron orbits. Unlike the usual Shubnikov-de Haas effect, these oscillations
are not affected by the temperature smearing of the Fermi distribution and can
therefore become dominant at high enough temperatures. We suggest that the slow
oscillations are a general feature of clean quasi-two-dimensional metals and
discuss possible applications of the phenomenon.Comment: 11 pages, 3 figure
Comparison of coherent and weakly incoherent transport models for the interlayer magnetoresistance of layered Fermi liquids
The interlayer magnetoresistance of layered metals in a tilted magnetic field
is calculated for two distinct models for the interlayer transport. The first
model involves coherent interlayer transport and makes use of results of
semi-classical or Bloch-Boltzmann transport theory. The second model involves
weakly incoherent interlayer transport where the electron is scattered many
times within a layer before tunneling into the next layer. The results are
relevant to the interpretation of experiments on angular-dependent
magnetoresistance oscillations (AMRO) in quasi-one- and quasi-two-dimensional
metals. We find that the dependence of the magnetoresistance on the direction
of the magnetic field is identical for both models except when the field is
almost parallel to the layers. An important implication of this result is that
a three-dimensional Fermi surface is not necessary for the observation of the
Yamaji and Danner oscillations seen in quasi-two- and quasi-one-dimensional
metals, respectively. A universal expression is given for the dependence of the
resistance at AMRO maxima and minima on the magnetic field and scattering time
(and thus the temperature). We point out three distinctive features of coherent
interlayer transport: (i) a beat frequency in the magnetic oscillations of
quasi-two-dimensional systems, (ii) a peak in the angular-dependent
magnetoresistance when the field is sufficiently large and parallel to the
layers, and (iii) a crossover from a linear to a quadratic field dependence for
the magnetoresistance when the field is parallel to the layers. Properties (i)
and (ii) are compared with published experimental data for a range of
quasi-two-dimensional organic metals and for Sr2RuO4.Comment: 21 pages, RevTeX + epsf, 4 figures. Published version. Subsection
added. References update
Magnetic field - temperature phase diagram of the organic conductor alpha-(BEDT-TTF)2KHg(SCN)4
We present systematic magnetic torque studies of the ``magnetic field -
temperature'' phase diagram of the layered organic conductor
alpha-(BEDT-TTF)2KHg(SCN)4 at fields nearly perpendicular and nearly parallel
to the highly conducting plane. The shape of the phase diagram is compared to
that predicted for a charge-density-wave system in a broad field range.Comment: 3 RevTEX pages, 3 PS figures, to be published in JETP Let
Orbital effect of a magnetic field on the low temperature state in the organic metal -(BEDT-TTF)KHg(SCN)
The effect of pressure on the B--T phase diagram of
-(BEDT-TTF)KHg(SCN) is studied. The measured phase lines can be
well described by a recent model of a charge-density wave system with varying
nesting conditions. A remarkable increase of the transition temperature with
magnetic field is found in a certain pressure and field range. We associate
this result with a dramatic enhancement of the orbital effect of magnetic field
due to a deterioration of the nesting conditions by pressure. Furthermore, we
present data which can be interpreted as a first sign of field-induced
charge-density waves.Comment: 9 pages, 5 figure
Incoherent interlayer transport and angular-dependent magnetoresistance oscillations in layered metals
The effect of incoherent interlayer transport on the interlayer resistance of a layered metal is considered. We find that for both quasi-one-dimensional and quasi-two-dimensional Fermi liquids the angular dependence of the magnetoresistance is essentially the same for coherent and incoherent transport. Consequently, the existence of a three-dimensional Fermi surface is not necessary to explain the oscillations in the magnetoresistance that are seen in many organic conductors as the field direction is varied. [S0031-9007(98)07660-1]
Sawtooth chemical potential oscillations in the strongly 2D organic metal κ-(BEDT-TTF)2I3 at high Landau level filling factors
In the strongly two-dimensional (2D) organic metal K-(BEDT-
TTF)(2)I-3, sawtooth oscillations of the chemical potential mu
are observed by means of Shubnikov-de Haas and de Haas-van
Alphen experiments. The sawtooth shape of these oscillations of
mu corresponds to the behaviour of a 2D canonical ensemble of
electrons. In contrast to preceding investigations, the simple
method described here probes mu, directly and reveals
oscillations of g with the quantum oscillation frequency F-0 =
13T. (C) 2002 Elsevier Science Ltd. All rights reserved
Electron correlations in the 2D organic metal κ-(BEDT-TTF)2I3 at high Landau level filling factors
In the two-dimensional (21)) multilayer organic metal kappa-
(BEDT-TTF)(2)I-3 strong electron correlations are present at
magnetic fields B > 12 T and temperatures T < 1 K. These
correlations manifest themselves in strong anomalous damping
effects of magnetoquantum oscillations at high magnetic fields,
which are controlled by the low Landau level filling factors v
< 3 in a part of the Fermi surface (FS). It is found that the
electron correlations capture all electrons of the FS,
including even the parts with very high v. (C) 2002 Elsevier
Science Ltd. All rights reserved