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Type-I superconductivity in noncentrosymmetric superconductor AuBe
The noncentrosymmetric superconductor AuBe have been investigated using the
magnetization, resistivity, specific heat, and muon-spin relaxation/rotation
measurements. AuBe crystallizes in the cubic FeSi-type B20 structure with
superconducting transition temperature observed at = 3.2 0.1 K.
The low-temperature specific heat data, (T), indicate a weakly-coupled
fully gapped BCS superconductivity with an isotropic energy gap
2 = 3.76, which is close to the BCS value of 3.52.
Interestingly, type-I superconductivity is inferred from the SR
measurements, which is in contrast with the earlier reports of type-II
superconductivity in AuBe. The Ginzburg-Landau parameter is = 0.4
1/. The transverse-field SR data transformed in the maximum
entropy spectra depicting the internal magnetic field probability distribution,
P(H), also confirms the absence of the mixed state in AuBe. The thermodynamic
critical field, , calculated to be around 259 Oe. The zero-field SR
results indicate that time-reversal symmetry is preserved and supports a
spin-singlet pairing in the superconducting ground state.Comment: 9 pages, 9 figure
Probing the superconducting ground state of the rare-earth ternary boride superconductors RuB ( = Lu,Y) using muon-spin rotation and relaxation
The superconductivity in the rare-earth transition metal ternary borides
RuB (where = Lu and Y) has been investigated using muon-spin
rotation and relaxation. Measurements made in zero-field suggest that
time-reversal symmetry is preserved upon entering the superconducting state in
both materials; a small difference in depolarization is observed above and
below the superconducting transition in both compounds, however this has been
attributed to quasistatic magnetic fluctuations. Transverse-field measurements
of the flux-line lattice indicate that the superconductivity in both materials
is fully gapped, with a conventional s-wave pairing symmetry and BCS-like
magnitudes for the zero-temperature gap energies. The electronic properties of
the charge carriers in the superconducting state have been calculated, with
effective masses and in the Lu
and Y compounds, respectively, with superconducting carrier densities
() m and ()
m. The materials have been classified according to the
Uemura scheme for superconductivity, with values for
of and , implying that
the superconductivity may not be entirely conventional in nature.Comment: 8 pages, 8 figure
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