36 research outputs found
Wang-MacDonald d-wave vortex cores observed in heavily overdoped BiSrCaCuO
Low magnetic field scanning tunneling spectroscopy of individual Abrikosov
vortices in heavily overdoped BiSrCaCuO unveils a
clear d-wave electronic structure of the vortex core, with a zero-bias
conductance peak at the vortex center that splits with increasing distance from
the core. We show that previously reported unconventional electronic
structures, including the low energy checkerboard charge order in the vortex
halo and the absence of a zero-bias conductance peak at the vortex center, are
direct consequences of short inter-vortex distance and consequent vortex-vortex
interactions prevailing in earlier experiments.Comment: Main text : 5 pages, 4 figures Supplemental material : 3 pages, 2
figure
Revisiting the vortex-core tunnelling spectroscopy in YBaCuO
The observation by scanning tunnelling spectroscopy (STS) of Abrikosov vortex
cores in the high-temperature superconductor YBaCuO (Y123)
has revealed a robust pair of electron-hole symmetric states at finite subgap
energy. Their interpretation remains an open question because theory predicts a
different signature in the vortex cores, characterised by a strong zero-bias
conductance peak. We present STS data on very homogeneous Y123 at 0.4 K
revealing that the subgap features do not belong to vortices: they are actually
observed everywhere along the surface with high spatial and energy
reproducibility, even in the absence of magnetic field. Detailed analysis and
modelling show that these states remain unpaired in the superconducting phase
and belong to an incoherent channel which contributes to the tunnelling signal
in parallel with the superconducting density of states.Comment: Final version with supplementary materia
Fingerprint of dynamical charge/spin correlations in the tunneling spectra of colossal magnetoresistive manganites
We present temperature-dependent scanning tunneling spectroscopy measurements
on () films with different degrees of biaxial
strain. A depletion in normalized conductance around the Fermi level is
observed both above and below the insulator-to-metal transition temperature
, for weakly as well as highly-strained films. This pseudogap-like
depletion globally narrows on cooling. The zero-bias conductance decreases on
cooling in the insulating phase, reaches a minimum close to and
increases on cooling in the metallic phase, following the trend of macroscopic
conductivity. These results support a recently proposed scenario in which
dynamical short-range antiferromagnetic/charge order correlations play a
preeminent role in the transport properties of colossal magnetoresistive
manganites [R. Yu \textit{et al}., Phys. Rev. B \textbf{77}, 214434 (2008)].Comment: 9 pages, 4 figure
Vortex-core spectroscopy of -wave cuprate high-temperature superconductors
The mechanism of high-temperature superconductivity remains one of the great
challenges of contemporary physics. Here, we review efforts to image the vortex
lattice in copper oxide-based high-temperature superconductors and to measure
the characteristic electronic structure of the vortex core of a -wave
superconductor using scanning tunneling spectroscopy.Comment: Main text : 7 pages, 8 figure
Scanning tunneling spectroscopy of high-temperature superconductors
Tunneling spectroscopy played a central role in the experimental verification
of the microscopic theory of superconductivity in the classical
superconductors. Initial attempts to apply the same approach to
high-temperature superconductors were hampered by various problems related to
the complexity of these materials. The use of scanning tunneling
microscopy/spectroscopy (STM/STS) on these compounds allowed to overcome the
main difficulties. This success motivated a rapidly growing scientific
community to apply this technique to high-temperature superconductors. This
paper reviews the experimental highlights obtained over the last decade. We
first recall the crucial efforts to gain control over the technique and to
obtain reproducible results. We then discuss how the STM/STS technique has
contributed to the study of some of the most unusual and remarkable properties
of high-temperature superconductors: the unusual large gap values and the
absence of scaling with the critical temperature; the pseudogap and its
relation to superconductivity; the unprecedented small size of the vortex cores
and its influence on vortex matter; the unexpected electronic properties of the
vortex cores; the combination of atomic resolution and spectroscopy leading to
the observation of periodic local density of states modulations in the
superconducting and pseudogap states, and in the vortex cores.Comment: To appear in RMP; 65 pages, 62 figure
Vortex lattice imaging and spectroscopic studies of flux lines by scanning tunneling microscopy
Wang-MacDonald d-wave vortex cores observed in heavily overdoped Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8+δ</sub>
Low magnetic field scanning tunneling spectroscopy of individual Abrikosov vortices in heavily overdoped Bi2Sr2CaCu2O8+δ unveils a clear d-wave electronic structure of the vortex core, with a zero-bias conductance peak at the vortex center that splits with increasing distance from the core. We show that previously reported unconventional electronic structures, including the low energy checkerboard charge order in the vortex halo and the absence of a zero-bias conductance peak at the vortex center, are direct consequences of short inter-vortex distance and consequent vortex-vortex interactions prevailing in earlier experiments