12,217 research outputs found
Effect of Magnetic field on the Pseudogap Phenomena in High-Tc Cuprates
We theoretically investigate the effect of magnetic field on the pseudogap
phenomena in High-Tc cuprates.
The obtained results well explain the experimental results including their
doping dependences.
In our previous paper (J. Phys. Soc. Jpn. 68 (1999) 2999.), we have shown
that the pseudogap phenomena observed in High-Tc cuprates are naturally
understood as a precursor of the strong coupling superconductivity. On the
other hand, there is an interpretation for the recent high field NMR
measurements to be an evidence denying the pairing scenarios for the pseudogap.
In this paper, we investigate the magnetic field dependence of NMR
on the basis of our formalism and show the interpretation to be inappropriate.
The results indicate that the value of the characteristic magnetic field
is remarkably large in case of the strong coupling
superconductivity, especially near the pseudogap onset temperature .
Therefore, the magnetic field dependences can not be observed and does
not vary when the strong pseudogap anomaly is observed. On the other hand,
is small in the comparatively weak coupling case and
varies when the weak pseudogap phenomena are observed.
These results properly explain the high magnetic field NMR experiments
continuously from under-doped to over-doped cuprates.
Moreover, we discuss the transport phenomena in the pseudogap phase. The
behaviors of the in-plane resistivity, the Hall coefficient and the c-axis
resistivity in the pseudogap phase are naturally understood by considering the
d-wave pseudogap
Magnetic Field Effect on the Pseudogap Temperature within Precursor Superconductivity
We determine the magnetic field dependence of the pseudogap closing
temperature T* within a precursor superconductivity scenario. Detailed
calculations with an anisotropic attractive Hubbard model account for a
recently determined experimental relation in BSCCO between the pseudogap
closing field and the pseudogap temperature at zero field, as well as for the
weak initial dependence of T* at low fields. Our results indicate that the
available experimental data are fully compatible with a superconducting origin
of the pseudogap in cuprate superconductors.Comment: 4 pages, 3 figure
Evidence for a preformed Cooper pair model in the pseudogap spectra of a Ca10(Pt4As8)(Fe2As2)5 single crystal with a nodal superconducting gap
For high-Tc superconductors, clarifying the role and origin of the pseudogap
is essential for understanding the pairing mechanism. Among the various models
describing the pseudogap, the preformed Cooper pair model is a potential
candidate. Therefore, we present experimental evidence for the preformed Cooper
pair model by studying the pseudogap spectrum observed in the optical
conductivity of a Ca10(Pt4As8)(Fe2As2)5 (Tc = 34.6 K) single crystal. We
observed a clear pseudogap structure in the optical conductivity and observed
its temperature dependence. In the superconducting (SC) state, one SC gap with
a gap size of {\Delta} = 26 cm-1, a scattering rate of 1/{\tau} = 360 cm-1 and
a low-frequency extra Drude component were observed. Spectral weight analysis
revealed that the SC gap and pseudogap are formed from the same Drude band.
This means that the pseudogap is a gap structure observed as a result of a
continuous temperature evolution of the SC gap observed below Tc. This provides
clear experimental evidence for the preformed Cooper pair model.Comment: 15 pages, 4 figure
Pseudogap in fermionic density of states in the BCS-BEC crossover of atomic Fermi gases
We study pseudogap behaviors of ultracold Fermi gases in the BCS-BEC
crossover region. We calculate the density of states (DOS), as well as the
single-particle spectral weight, above the superfluid transition temperature
including pairing fluctuations within a -matrix approximation.
We find that DOS exhibits a pseudogap structure in the BCS-BEC crossover
region, which is most remarkable near the unitarity limit. We determine the
pseudogap temperature at which the pseudogap structure in DOS disappears.
We also introduce another temperature at which the BCS-like
double-peak structure disappears in the spectral weight. While one finds
in the BCS regime, becomes higher than in the
crossover and BEC regime. We also determine the pseudogap region in the phase
diagram in terms of temperature and pairing interaction.Comment: 6 pages, 4 figures, Proceedings of QFS 200
The pseudogap in high-temperature superconductors: an experimental survey
We present an experimental review of the nature of the pseudogap in the
cuprate superconductors. Evidence from various experimental techniques points
to a common phenomenology. The pseudogap is seen in all high temperature
superconductors and there is general agreement on the temperature and doping
range where it exists. It is also becoming clear that the superconducting gap
emerges from the normal state pseudogap. The d-wave nature of the order
parameter holds for both the superconducting gap and the pseudogap. Although an
extensive body of evidence is reviewed, a consensus on the origin of the
pseudogap is as lacking as it is for the mechanism underlying high temperature
superconductivity.Comment: review article, 54 pages, 50 figure
Stripes and electronic quasiparticles in the pseudogap state of cuprate superconductors
This article is devoted to a discussion of stripe and electron-nematic order
and their connection to electronic properties in the pseudogap regime of
copper-oxide superconductors. We review basic properties of these
symmetry-breaking ordering phenomena as well as proposals which connect them to
quantum-oscillation measurements. Experimental data indicate that these orders
are unlikely to be the cause of the pseudogap phenomenon, implying that they
occur on top of the pseudogap state which itself is of different origin.
Specifically, we discuss the idea that the non-superconducting pseudogap ground
state hosts electron-like quasiparticles which coexist with a spin liquid,
realizing a variant of a fractionalized Fermi liquid. We speculate on how
stripe order in such a pseudogap state might offer a consistent description of
ARPES, NMR, quantum-oscillation, and transport data.Comment: 15 pages, 6 figs. Article prepared for a Physica C special issue on
"Stripes and Electronic Liquid Crystals
Pseudogap from ARPES experiment: three gaps in cuprates and topological superconductivity
A term first coined by Mott back in 1968 a `pseudogap' is the depletion of
the electronic density of states at the Fermi level, and pseudogaps have been
observed in many systems. However, since the discovery of the high temperature
superconductors (HTSC) in 1986, the central role attributed to the pseudogap in
these systems has meant that by many researchers now associate the term
pseudogap exclusively with the HTSC phenomenon. Recently, the problem has got a
lot of new attention with the rediscovery of two distinct energy scales
(`two-gap scenario') and charge density waves patterns in the cuprates. Despite
many excellent reviews on the pseudogap phenomenon in HTSC, published from its
very discovery up to now, the mechanism of the pseudogap and its relation to
superconductivity are still open questions. The present review represents a
contribution dealing with the pseudogap, focusing on results from angle
resolved photoemission spectroscopy (ARPES) and ends up with the conclusion
that the pseudogap in cuprates is a complex phenomenon which includes at least
three different `intertwined' orders: spin and charge density waves and
preformed pairs, which appears in different parts of the phase diagram. The
density waves in cuprates are competing to superconductivity for the electronic
states but, on the other hand, should drive the electronic structure to
vicinity of Lifshitz transition, that could be a key similarity between the
superconducting cuprates and iron based superconductors. One may also note that
since the pseudogap in cuprates has multiple origins there is no need to recoin
the term suggested by Mott.Comment: invited review, more info at http://www.imp.kiev.ua/~kor
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