1,121 research outputs found
Correlation between and anisotropic scattering in TlBaCuO
Angle-dependent magnetoresistance measurements are used to determine the
isotropic and anisotropic components of the transport scattering rate in
overdoped TlBaCuO for a range of values between 15K
and 35K. The size of the anisotropic scattering term is found to scale linearly
with , establishing a link between the superconducting and normal state
physics. Comparison with results from angle resolved photoemission spectroscopy
indicates that the transport and quasiparticle lifetimes are distinct.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Optical response of high- cuprates: possible role of scattering rate saturation and in-plane anisotropy
We present a generalized Drude analysis of the in-plane optical conductivity
(,) in cuprates taking into account the effects of
in-plane anisotropy. A simple ansatz for the scattering rate
(,), that includes anisotropy, a quadratic frequency
dependence and saturation at the Mott-Ioffe-Regel limit, is able to reproduce
recent normal state data on an optimally doped cuprate over a wide frequency
range. We highlight the potential importance of including anisotropy in the
full expression for (,) and challenge previous
determinations of () in which anisotropy was neglected and
() was indicated to be strictly linear in frequency over a wide
frequency range. Possible implications of our findings for understanding
thermodynamic properties and self-energy effects in high- cuprates will
also be discussed.Comment: 8 pages, 7 figures. To be published in Physical Review
Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field
We report measurements of the temperature dependent components of the
magnetic penetration depth {\lambda}(T) in single crystal samples of
YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We
observe a downturn in {\lambda}(T) at low temperatures for currents flowing
along the b and c axes but not along the a axis. The downturn in {\lambda}_b is
suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy
of {\lambda}(T) likely result from proximity induced superconducting on the CuO
chains, however we also discuss the possibility that a significant part of the
anisotropy might originate from the CuO2 planes.Comment: 5 page
Violation of the isotropic- approximation in overdoped La_{2-x}Sr_xCuO_4
Magnetotransport measurements on the overdoped cuprate La_{1.7}Sr_{0.3}CuO_4
are fitted using the Ong construction and band parameters inferred from
angle-resolved photoemission. Within a band picture, the low temperature Hall
data can only be fitted satisfactorily by invoking strong basal-plane
anisotropy in the mean-free-path . This violation of the isotropic-
approximation supports a picture of dominant small-angle elastic scattering in
cuprates due to out-of-plane substitutional disorder. We show that both band
anisotropy and anisotropy in the elastic scattering channel strongly
renormalize the Hall coefficient in overdoped La_{2-x}Sr_xCuO_4 over a wide
doping and temperature range.Comment: 4 pages, 4 figure
A Tale of Two Metals: contrasting criticalities in the pnictides and hole-doped cuprates
The iron-based high temperature superconductors share a number of
similarities with their copper-based counterparts, such as reduced
dimensionality, proximity to states of competing order, and a critical role for
3d electron orbitals. Their respective temperature-doping phase diagrams also
contain certain commonalities that have led to claims that the metallic and
superconducting properties of both families are governed by their proximity to
a quantum critical point (QCP) located inside the superconducting dome. In this
review, we critically examine these claims and highlight significant
differences in the bulk physical properties of both systems. While there is now
a large body of evidence supporting the presence of a (magnetic) QCP in the
iron pnictides, the situation in the cuprates is much less apparent, at least
for the end point of the pseudogap phase. We argue that the opening of the
normal state pseudogap in cuprates, so often tied to a putative QCP, arises
from a momentum-dependent breakdown of quasiparticle coherence that sets in at
much higher doping levels but which is driven by the proximity to the Mott
insulating state at half filling. Finally, we present a new scenario for the
cuprates in which this loss of quasiparticle integrity and its evolution with
momentum, temperature and doping plays a key role in shaping the resultant
phase diagram.Comment: This key issues review is dedicated to the memory of Dr. John Loram
whose pioneering measurements, analysis and ideas inspired much of its
conten
Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals
Studies of interlayer transport in layered metals have generally made use of
zero temperature conductivity expressions to analyze angle-dependent
magnetoresistance oscillations (AMRO). However, recent high temperature AMRO
experiments have been performed in a regime where the inclusion of finite
temperature effects may be required for a quantitative description of the
resistivity. We calculate the interlayer conductivity in a layered metal with
anisotropic Fermi surface properties allowing for finite temperature effects.
We find that resistance maxima are modified by thermal effects much more
strongly than resistance minima. We also use our expressions to calculate the
interlayer resistivity appropriate to recent AMRO experiments in an overdoped
cuprate which led to the conclusion that there is an anisotropic, linear in
temperature contribution to the scattering rate and find that this conclusion
is robust.Comment: 8 pages, 4 figure
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