Physical Properties of Li2Pd3B and Li2Pt3B Superconductors

2007 ◽  
Vol 561-565 ◽  
pp. 2079-2082 ◽  
Author(s):  
Hiroyuki Takeya ◽  
Shigeru Kasahara ◽  
Mohammed El Massalami ◽  
Takashi Mochiku ◽  
Kazuto Hirata ◽  
...  
Keyword(s):  
Specific Heat ◽  
Relaxation Method ◽  
Zero Magnetic Field ◽  
Bcs Theory ◽  
Superconducting Gap ◽  
Electronic Specific Heat ◽  
Superconducting Transition ◽  
Critical Fields ◽  
Resistivity Measurements ◽  
Upper Critical Fields

Superconductivity in two Li-containing compounds of Li2Pd3B and Li2Pt3B was recently discovered. These materials, showing the superconducting transition at 7.2 K and 2.6 K, respectively, have the same cubic structure (P4332) composed of distorted octahedrons without mirror or inversion symmetry along any directions. This is a very interesting feature of those materials in relation to the symmetry of superconductivity. Resistivity measurements in magnetic fields gave their upper critical fields, Hc2(0) = 45 kOe and 19 kOe, respectively. Their specific heat was measured using a heat-pulse relaxation method. The Sommerfeld coefficient (γ) and Debye temperature (θD) terms of Li2Pd3B were given as γ=9.5 mJmol-1K-2 and θD=228 K . The value of C/γT at Tc was calculated to be 1.7. In the same manner, those parameters were described for Li2Pt3B as γ=9.6 mJmol-1K-2, θD=240 K, and C/γTc =0.75, respectively. Since C/γTC in the weakcoupling limit by the BCS theory is 1.43, the value of 1.7 for Li2Pd3B is slightly higher. The electronic specific heat of Li2Pd3B at a zero magnetic field follows the typical exponetial behavior discribed in the BCS theory, while that of Li2Pt3B shows quadratic behavior. This result suggests the line nodes exist in the superconducting gap of Li2Pt3B driven by the spin-orbit interaction.

Superconductivity at Tc = 36.5 K in Na-Substituted SrFe2As2 Single Crystals

2014 ◽  
Vol 95 ◽  
pp. 150-155 ◽  
Author(s):  
Larysa Shlyk ◽  
Markus Bischoff ◽  
Eva Rose ◽  
Rainer Niewa
Keyword(s):  
Single Crystals ◽  
Anisotropy Ratio ◽  
Superconducting Transition ◽  
Critical Fields ◽  
Superconducting Cuprates ◽  
Resistivity Measurements ◽  
Relaxation Measurements ◽  
Narrow Width ◽  
Upper Critical Fields

We report superconductivity, which is achieved in Sr1-xNaxFe2As2 at Tc = 36.5 K for x = 0.47. Single crystals of Na-substituted SrFe2As2 up to 2 × 2 mm2 were grown from NaF flux. The superconducting transition temperature with a narrow width less than 2 K, confirmed by both magnetic and resistivity measurements, indicates the high quality of our samples. The upper critical fields (0) = 87 T and (0) = 217.5 T are extremely high. The anisotropy ratio γ ~ 2.5 is close to that of other hole-or electron-doped 122 phases but lower than γ ~ 4.3 – 5 of phases from the 1111 series and much lower than γ ~ 7 – 10 of superconducting cuprates. Magnetic relaxation measurements, which are consistent with the collective pinning model, reveal that the flux-creep rate in Na substituted 122 SrFe2As2 is smaller than in 1111 type iron pnictides.

scholarly journals Potassium-Doped Para-Terphenyl: Structure, Electrical Transport Properties and Possible Signatures of a Superconducting Transition

2020 ◽  
Vol 5 (4) ◽  
pp. 78
Author(s):  
Nicola Pinto ◽  
Corrado Di Nicola ◽  
Angela Trapananti ◽  
Marco Minicucci ◽  
Andrea Di Cicco ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Chemical Method ◽  
Preliminary Evidence ◽  
Superconducting Gap ◽  
Superconducting Transition ◽  
Electrical Transport Properties ◽  
High Tc ◽  
Resistivity Measurements

Preliminary evidence for the occurrence of high-TC superconductivity in alkali-doped organic materials, such as potassium-doped p-terphenyl (KPT), were recently obtained by magnetic susceptibility measurements and by the opening of a large superconducting gap as measured by ARPES and STM techniques. In this work, KPT samples have been synthesized by a chemical method and characterized by low-temperature Raman scattering and resistivity measurements. Here, we report the occurrence of a resistivity drop of more than 4 orders of magnitude at low temperatures in KPT samples in the form of compressed powder. This fact was interpreted as a possible sign of a broad superconducting transition taking place below 90 K in granular KPT. The granular nature of the KPT system appears to be also related to the 20 K broadening of the resistivity drop around the critical temperature.

Publisher’s Note: Specific heat and upper critical fields in KFe2As2single crystals [Phys. Rev. B85, 134533 (2012)]

2012 ◽  
Vol 85 (17) ◽  
Author(s):  
M. Abdel-Hafiez ◽  
S. Aswartham ◽  
S. Wurmehl ◽  
V. Grinenko ◽  
C. Hess ◽  
...  
Keyword(s):  
Specific Heat ◽  
Critical Fields ◽  
Upper Critical Fields

scholarly journals Specific heat and upper critical fields in KFe2As2single crystals

2012 ◽  
Vol 85 (13) ◽  
Author(s):  
M. Abdel-Hafiez ◽  
S. Aswartham ◽  
S. Wurmehl ◽  
V. Grinenko ◽  
C. Hess ◽  
...  
Keyword(s):  
Specific Heat ◽  
Critical Fields ◽  
Upper Critical Fields

Superconductivity of tin isotopes

1951 ◽  
Vol 47 (4) ◽  
pp. 811-819 ◽  
Author(s):  
J. M. Lock ◽  
A. B. Pippard ◽  
D. Shoenberg
Keyword(s):  
Transition Temperature ◽  
Magnetic Fields ◽  
Specific Heat ◽  
Critical Field ◽  
Electronic Specific Heat ◽  
Transition Temperatures ◽  
Superconducting Transition ◽  
Critical Magnetic Fields ◽  
The Law

AbstractDetailed measurements have been made of the superconducting transition temperatures and critical magnetic fields of the tin isotopes of mass 116, 120 and 124. The transition temperature varies with isotopic mass according to the law Tc ∞ M−n, with n = 0·462 ± 0·014, a result very similar to that already found in mercury. The critical field curves of isotopes 116 and 124 are geometrically similar, in the sense that both many be represented by the same equation, Hc/Ho = f(T/Tc), with the same ratio Ho/Tc for both. It is deduced that the electronic specific heat in normal tin varies only slowly, if at all, with isotopic mass. The variation of Tc and Ho with M is very close to that predicted by Fröhlich and Bardeen.

scholarly journals Investigation of a CDDW Hamiltonian to Explore Possibility of Magneto-Quantum Oscillations in Electronic Specific Heat of Hole-Doped Cuprates

2010 ◽  
Vol 2010 ◽  
pp. 1-11
Author(s):  
Partha Goswami ◽  
Manju Rani
Keyword(s):  
Specific Heat ◽  
Chemical Potential ◽  
Density Wave ◽  
Mean Field ◽  
Anisotropy Parameter ◽  
Zero Magnetic Field ◽  
Electronic Specific Heat ◽  
Mean Field Model ◽  
Quantum Oscillations ◽  
Disorder Potential

We investigate a chiral d-density wave (CDDW) mean field model Hamiltonian in the momentum space suitable for the hole-doped cuprates, such as YBCO, in the pseudogap phase to obtain the Fermi surface (FS) topologies, including the anisotropy parameter() and the elastic scattering by disorder potential (). For , with the chemical potential eV for 10% doping level and (where eV is the first neighbor hopping), at zero/non-zero magnetic field (), the FS on the first Brillouin zone is found to correspond to electron pockets around antinodal regions and barely visible patches around nodal regions. For , we find Pomeranchuk distortion of FS. We next relate our findings regarding FS to the magneto-quantum oscillations in the electronic specific heat. Since the nodal quasiparticle energy values for are found to be greater than for , the origin of the oscillations for nonzero corresponds to the Fermi pockets around antinodal regions. The oscillations are shown to take place in the weak disorder regime (eV) only.

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