130 research outputs found
Multiple Quantum Oscillations in the de Haas van Alphen Spectra of the Underdoped High Temperature Superconductor YBa_2Cu_3O_6.5
By improving the experimental conditions and extensive data accumulation, we
have achieved very high-precision in the measurements of the de Haas-van Alphen
effect in the underdoped high-temperature superconductor
YBaCuO. We find that the main oscillation, so far believed
to be single-frequency, is composed of three closely spaced frequencies. We
attribute this to bilayer splitting and warping of a single quasi-2D Fermi
surface, indicating that \emph{c}-axis coherence is restored at low temperature
in underdoped cuprates. Our results do not support the existence of a larger
frequency of the order of 1650 T reported recently in the same compound [S.E.
Sebastian {\it et al}., Nature {\bf 454}, 200 (2008)]
Magnetoresistance of semi-metals: the case of antimony
Large unsaturated magnetoresistance has been recently reported in numerous
semi-metals. Many of them have a topologically non-trivial band dispersion,
such as Weyl nodes or lines. Here, we show that elemental antimony displays the
largest high-field magnetoresistance among all known semi-metals. We present a
detailed study of the angle-dependent magnetoresistance and use a
semi-classical framework invoking an anisotropic mobility tensor to fit the
data. A slight deviation from perfect compensation and a modest variation with
magnetic field of the components of the mobility tensor are required to attain
perfect fits at arbitrary strength and orientation of magnetic field in the
entire temperature window of study. Our results demonstrate that large orbital
magnetoresistance is an unavoidable consequence of low carrier concentration
and the sub-quadratic magnetoresistance seen in many semi-metals can be
attributed to field-dependent mobility, expected whenever the disorder
length-scale exceeds the Fermi wavelength.Comment: Supplementary material on reques
An electronic instability in bismuth far beyond the quantum limit
We present a transport study of semi-metallic bismuth in presence of a
magnetic field applied along the trigonal axis extended to 55 T for electric
conductivity and to 45 T for thermoelectric response. The results uncover a new
field scale at about 40 T in addition to the previously detected ones. Large
anomalies in all transport properties point to an intriguing electronic
instability deep in the ultraquantum regime. Unexpectedly, both the sheer
magnitude of conductivity and its metallic temperature dependence are enhanced
by this instability.Comment: 5 pages, 4 figure
Fermi liquid behavior of the in-plane resistivity in the pseudogap state of YBa_2Cu_4O_8
Our knowledge of the ground state of underdoped hole-doped cuprates has
evolved considerably over the last few years. There is now compelling evidence
that inside the pseudogap phase, charge order breaks translational symmetry
leading to a reconstructed Fermi surface made of small pockets. Quantum
oscillations, [Doiron-Leyraud N, et al. (2007) Nature 447:564-568], optical
conductivity [Mirzaei SI, et al. (2013) Proc Natl Acad Sci USA 110:5774-5778]
and the validity of Wiedemann-Franz law [Grissonnache G, et al. (2016) Phys.
Rev. B 93:064513] point to a Fermi liquid regime at low temperature in the
underdoped regime. However, the observation of a quadratic temperature
dependence in the electrical resistivity at low temperatures, the hallmark of a
Fermi liquid regime, is still missing. Here, we report magnetoresistance
measurements in the magnetic-field-induced normal state of underdoped
YBa_2Cu_4O_8 which are consistent with a T^2 resistivity extending down to 1.5
K. The magnitude of the T^2 coefficient, however, is much smaller than expected
for a single pocket of the mass and size observed in quantum oscillations,
implying that the reconstructed Fermi surface must consist of at least one
additional pocket.Comment: Main + SI : published versio
de Haas-van Alphen oscillations in the underdoped cuprate YBaCuO
The de Haas-van Alphen effect was observed in the underdoped cuprate
YBaCuO via a torque technique in pulsed magnetic fields up to
59 T. Above an irreversibility field of 30 T, the magnetization exhibits
clear quantum oscillations with a single frequency of 540 T and a cyclotron
mass of 1.76 times the free electron mass, in excellent agreement with
previously observed Shubnikov-de Haas oscillations. The oscillations obey the
standard Lifshitz-Kosevich formula of Fermi-liquid theory. This thermodynamic
observation of quantum oscillations confirms the existence of a well-defined,
close and coherent, Fermi surface in the pseudogap phase of cuprates.Comment: published versio
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