88 research outputs found
Perspective on the muon-spin rotation/relaxation under hydrostatic pressure
Pressure, together with temperature, electric and magnetic fields, alters the
system and allows to investigate the fundamental properties of the matter.
Under applied pressure the interatomic distances shrink, which modify
interactions between atoms and may lead to appearance of a new (sometime
exotic) physical properties as, e.g., pressure induced phase transition(s);
quantum critical points(s), new structural, magnetic and/or superconducting
states; changes of the temperature evolution and the symmetry of the order
parameter(s) etc. The muon-spin rotation/relaxation (SR) appears to be a
commonly used powerful technique allowing to study the magnetic and
superconducting responses of various materials under extreme conditions. At
present, SR experiments might be performed under the high magnetic field
up to T, temperatures down to mK and hydrostatic
pressure up to GPa. In the following Perspective paper the
requirements to the SR under pressure experiments, the existing
high-pressure muon facility at the Paul Scherrer Institute (Switzerland), and
selected experimental results obtained by using the SR under pressure
technique are discussed.Comment: 14 pages, 14 figure
Two-gap superconductivity in MoGa and its evolution upon the V substitution
Zero-field and transverse-field muon spin rotation/relaxation (SR)
experiments were undertaken in order to elucidate microscopic properties of a
strongly-coupled superconductor MoGa with K.
The upper critical field extracted from the transverse-field SR data
exhibits significant reduction with respect to the data from thermodynamic
measurements indicating the coexistence of two independent length scales in the
superconducting state. Accordingly, the temperature-dependent magnetic
penetration depth of MoGa is described using the model, in which
two s-wave superconducting gaps are assumed. The V for Mo substitution in the
parent compound leads to the complete suppression of one superconducting gap,
and MoVGa is well described within the single s-wave gap scenario.
The reduction in the superfluid density and the evolution of the
low-temperature resistivity upon the V substitution indicate the emergence of a
competing state in MoVGa that may be responsible for the closure
of one of the superconducting gaps
Superconductivity of Bi-III phase of elemental Bismuth: insights from Muon-Spin Rotation and Density Functional Theory
Using muon-spin rotation the pressure-induced superconductivity in the Bi-III
phase of elemental Bismuth (transition temperature K) was
investigated. The Ginzburg-Landau parameter
( is the magnetic penetration depth, is the coherence length)
was estimated which is the highest among single element superconductors. The
temperature dependence of the superconducting energy gap []
reconstructed from deviates from the weak-coupled BCS
prediction. The coupling strength was
estimated thus implying that Bi-III stays within the strong coupling regime.
The Density Functional Theory calculations suggest that superconductivity in
Bi-III could be described within the Eliashberg approach with the
characteristic phonon frequency meV. An alternative
pairing mechanism to the electron-phonon coupling involves the possibility of
Cooper pairing induced by the Fermi surface nesting.Comment: 5 pages, 4 figure
On the superconducting nature of the Bi-II phase of elemental Bismuth
The superconductivity in the Bi-II phase of elemental Bismuth (transition
temperature K at pressure GPa) was studied
experimentally by means of the muon-spin rotation as well as theoretically by
using the Eliashberg theory in combination with Density Functional Theory
calculations. Experiments reveal that Bi-II is a type-I superconductor with a
zero temperature value of the thermodynamic critical field ~mT. The Eliashberg theory approach provides a good agreement
with the experimental and the temperature evolution of .
The estimated value for the retardation (coupling) parameter ( is the logarithmically
averaged phonon frequency) suggests that Bi-II is an intermediately-coupled
superconductor.Comment: 6 pages, 2 figure
Microscopic co-existence of superconductivity and magnetism in Ba1-xKxFe2As2
It is widely believed that, in contrast to its electron doped counterparts,
the hole doped compound Ba1-xKxFe2As2 exhibits a mesoscopic phase separation of
magnetism and superconductivity in the underdoped region of the phase diagram.
Here, we report a combined high-resolution x-ray powder diffraction and volume
sensitive muon spin rotation study of underdoped Ba1-xKxFe2As2 (0 \leq x \leq
0.25) showing that this paradigm is wrong. Instead we find a microscopic
coexistence of the two forms of order. A competition of magnetism and
superconductivity is evident from a significant reduction of the magnetic
moment and a concomitant decrease of the magneto-elastically coupled
orthorhombic lattice distortion below the superconducting phase transition.Comment: 4 pages, 4 figure
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