3 research outputs found
Fully Gapped Superconducting State Based on a High Normal State Quasiparticle Density of States in BaKFeAs Single Crystals
We report the specific heat (SH) measurements on single crystals of hole
doped -based superconductor . It is found that
the electronic SH coefficient is not temperature dependent and
increases almost linearly with the magnetic field in low temperature region.
These point to a fully gapped superconducting state. Surprisingly the sharp SH
anomaly reaches a value of 98 suggesting a
very high normal state quasiparticle density of states (). A detailed analysis reveals that the cannot be
fitted with a single gap of s-wave symmetry due to the presence of a hump in
the middle temperature region. However, our data indicate that the dominant
part of the superconducting condensate is induced by an s-wave gap with the
magnitude of about 6 meV.Comment: 5 pages, 5 figure
Role of multiband effects and electron-hole asymmetry in the superconductivity and normal state properties of Ba(FeCo)As
We report a systematic investigation, together with a theoretical analysis,
of the resistivity and Hall effect in single crystals of
Ba(FeCo)As, over a wide doping range. We find a
surprisingly great disparity between the relaxation rates of the holes and the
electrons, in excess of an order of magnitude in the low-doping,
low-temperature regime. The ratio of the electron to hole mobilities diminishes
with temperature and doping (away from the magnetically ordered state) and
becomes more conventional. We also find a straightforward explanation of the
large asymmetry (compared to cuprates) of the superconducting dome: in the
underdoped regime the decisive factor is the competition between AF and
superconductivity (SC), while in the overdoped regime the main role is played
by degradation of the nesting that weakens the pairing interaction. Our results
indicate that spin-fluctuations due to interband electron-hole scattering play
a crucial role not only in the superconducting pairing, but also in the normal
transport.Comment: 4 pages, 4 figure
Pairing symmetry and properties of iron-based high temperature superconductors
Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of the system. The quasiparticle gap falls into three
categories: full, nodal and gapless. The nodal-gap states show conventional
Volovik effect even for on-site pairing. The gapless states are odd in orbital
space, have a negative superfluid density and are therefore unstable. In
connection to experiments we proposed possible pairing states and implications
for the pairing mechanism.Comment: 4 pages, 1 table, 2 figures, polished versio