264 research outputs found
Magnetic Field Induced Coherence-Incoherence Crossover in the Interlayer Conductivity of a Layered Organic Metal
The angle-dependent interlayer magnetoresistance of the layered organic metal
-(BEDT-TTF)KHg(SCN) is found to undergo a dramatic change from
the classical conventional behavior at low magnetic fields to an anomalous one
at high fields. This field-induced crossover and its dependence on the sample
purity and temperature imply the existence of two parallel channels in the
interlayer transport: a classical Boltzmann conductivity and an
incoherent channel . We propose a simple model for
explaining its metallic temperature dependence and low sensitivity to the
inplane field component.Comment: 5 page
Theory of the Shubnikov-de Haas effect in quasi-two-dimensional metals
The Shubnikov - de Haas effect in quasi-two-dimensional normal metals is
studied. The interlayer conductivity is calculated using the Kubo formula. The
electron scattering on short-range is considered in the self-consistent Born
approximation. The result obtained differs from that derived from the Boltzmann
transport equation. This difference is shown to be a general feature of
conductivity in magnetic field. A detailed description of the two new
qualitative effects -- the field-dependent phase shift of beats and of the slow
oscillations of conductivity is provided. The results obtained are applicable
to strongly anisotropic organic metals and to other quasi-two-dimensional
compounds.Comment: 10 page
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
Angular magnetoresistance oscillations in bilayers in tilted magnetic fields
Angular magnetoresistance oscillations (AMRO) were originally discovered in
organic conductors and then found in many other layered metals. It should be
possible to observe AMRO to semiconducting bilayers as well. Here we present an
intuitive geometrical interpretation of AMRO as the Aharonov-Bohm interference
effect, both in real and momentum spaces, for balanced and imbalanced bilayers.
Applications to the experiments with bilayers in tilted magnetic fields in the
metallic state are discussed. We speculate that AMRO may be also observed when
each layer of the bilayer is in the composite-fermion state.Comment: 4 pages, 5 figures, Proceedings of EP2DS-16. V.2: figures corrected,
one reference added. V3: one reference adde
Direct evidence for superconductivity in the organic charge density-wave compound alpha-(BEDT-TTF)_2KHg(SCN)_4 under hydrostatic pressure
We present direct evidence of a superconducting state existing in the title
compound below 300 mK under quasi-hydrostatic pressure. The superconducing
transition is observed in the whole pressure range studied, 0 < P < 4 kbar.
However, the character of the transition drastically changes with suppressing
the charge-density wave state.Comment: 2 pages, 2 figure
Sensitivity of the interlayer magnetoresistance of layered metals to intralayer anisotropies
Many of the most interesting and technologically important electronic
materials discovered in the past two decades have two common features: a
layered crystal structure and strong interactions between electrons. Two of the
most fundamental questions about such layered metals concern the origin of
intralayer anisotropies and the coherence of interlayer charge transport. We
show that angle dependent magnetoresistance oscillations (AMRO) are sensitive
to anisotropies around an intralayer Fermi surface. Hence, AMRO can be a probe
of intralayer anisotropies that is complementary to angle-resolved
photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM).
However, AMRO are not very sensitive to the coherence of the interlayer
transport. We illustrate this with comparisons to recent AMRO experiments on an
overdoped cuprate.Comment: 7 pages, 3 figure
An analytically solvable model of the effect of magnetic breakdown on angle-dependent magnetoresistance in a quasi-two-dimensional metal
We have developed an analytical model of angle-dependent magnetoresistance
oscillations (AMROs) in a quasi-two-dimensional metal in which magnetic
breakdown occurs. The model takes account of all the contributions from
quasiparticles undergoing both magnetic breakdown and Bragg reflection at each
junction and allows extremely efficient simulation of data which can be
compared with recent experimental results on the organic metal
kappa-ET2Cu(NCS)2. AMROs resulting from both closed and open orbits emerge
naturally at low field, and the model enables the transition to breakdown-AMROs
with increasing field to be described in detail.Comment: 4 pages, 3 figure
Magnetotransport evidence of irreversible spin reorientation in the collinear antiferromagnetic state of underdoped
We make use of the strong spin-charge coupling in the electron-doped cuprate
to probe changes in its spin
system via magnetotransport measurements. We present a detailed study of the
out-of-plane magnetoresistance in underdoped single crystals of this compound,
including the nonsuperconducting, , and
superconducting, , compositions. Special focus is put
on the dependence of the magnetoresistance on the field orientation in the
plane of the CuO layers. In addition to the kink at the field-induced
transition between the noncollinear and collinear antiferromagnetic
configurations, a sharp irreversible feature is found in the angle-dependent
magnetoresistance of all samples in the high-field regime, at field
orientations around the Cu--O--Cu direction. The obtained behavior can be
explained in terms of field-induced reorientation of Cu spins within the
collinear antiferromagnetic state. It is, therefore, considered as an
unambiguous indication of the long-range magnetic order
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