Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSuperconducting Properties of BaBi$_{3}$
398
0
0.0
(
0
)
Added by
Neel Haldolaarachchige
Publication date
2014
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We report the superconducting properties of single crystals of the intermetallic perovskite-related compound BaBi$_{3}$. The superconducting transition temperature ($T_{c}=5.82$~K) was obtained from heat capacity measurements. Using the measured values for the critical fields $H_{c1}, H_{c2}$, and the specific heat $C$, we estimate the thermodynamic critical field $H_{c}$(0), coherence length $xi$(0), Debye temperature $Theta _{D}$ and coupling constant $lambda _{ep}$. $Delta C/gamma T_{c}$ and $lambda _{ep}$ suggest that BaBi$_{3}$ is a moderately coupled superconductor and $gamma $ suggests an enhanced density of states at the Fermi level. Electronic band structure calculations show a complex Fermi surface and a moderately high DOS at the Fermi level. Further analysis of the electronic specific heat shows that the superconducting properties are dominated by s-wave gap.
rate research
Read More
We report the superconducting properties of the K$_{x}$WO$_{3}$ tetragonal tungsten bronze. The highest superconducting transition temperature ($T_{c}=2.1$K) was obtained for K$_{0.38}$WO$_{3}$. $T_{c}$ decreases linearly with increasing K content. Using the measured values for the upper critical field $H_{c2}$, and the specific heat $C$, we estimate the orbital critical field $H_{c2}$(0), coherence length $xi$(0), Debye temperature $Theta _{D}$ and coupling constant $lambda _{ep}$. The magnitude of the specific heat jump at $T_{c}$ suggests that the K$_{x}$WO$_{3}$ tetragonal tungsten bronze is a weakly-coupled superconductor. The superconducting phase diagram of the doped tungsten bronze family is presented.
We report the magnetotransport properties of thin polycrystalline films of the recently discovered non-oxide perovskite superconductor MgCNi3. CNi3 precursor films were deposited onto sapphire substrates and subsequently exposed to Mg vapor at 700 C. We report transition temperatures (Tc) and critical field values (Hc2) of MgCNi3 films ranging in thickness from 7.5 nm to 100 nm. Films thicker than ~40 nm have a Tc ~ 8 K, and an upper critical field Hc2 ~ 14 T, which are both comparable to that of polycrystalline powders. Hall measurements in the normal state give a carrier density, n =-4.2 x 10^22 cm^-3, that is approximately 4 times that reported for bulk samples.
This review paper illustrates the main normal and superconducting state properties of magnesium diboride, a material known since early 1950s, but recently discovered to be superconductive at a remarkably high critical temperature Tc=40K for a binary compound. What makes MgB2 so special? Its high Tc, simple crystal structure, large coherence lengths, high critical current densities and fields, transparency of grain boundaries to current promises that MgB2 will be a good material for both large scale applications and electronic devices. During the last seven month, MgB2 has been fabricated in various forms, bulk, single crystals, thin films, tapes and wires. The largest critical current densities >10MA/cm2 and critical fields 40T are achieved for thin films. The anisotropy ratio inferred from upper critical field measurements is still to be resolved, a wide range of values being reported, between 1.2 and 9. Also there is no consensus about the existence of a single anisotropic or double energy gap. One central issue is whether or not MgB2 represents a new class of superconductors, being the tip of an iceberg who awaits to be discovered. Up to date MgB2 holds the record of the highest Tc in its class. However, the discovery of superconductivity in MgB2 revived the interest in non-oxides and initiated a search for superconductivity in related materials, several compounds being already announced to become superconductive: TaB2, BeB2.75, C-S composites, and the elemental B under pressure.
We report on structural and superconducting properties of La(3-x)R(x)Ni2B2N3 where La is substituted by the magnetic rare-earth elements Ce, Pr, Nd. The compounds Pr3Ni2B2N3 and Nd3Ni2B2N3 are characterized for the first time. Powder X-ray diffraction confirmed all samples R3Ni2B2N3 with R = La, Ce, Pr, Nd and their solid solutions to crystallize in the body centered tetragonal La3Ni2B2N3 structure type. Superconducting and magnetic properties of La(3-x)R(x)Ni2B2N3 were studied by resistivity, specific heat and susceptibility measurements. While La3Ni2B2N3 has a superconducting transition temperature Tc ~ 14 K, substitution of La by Ce, Pr, and Nd leads to magnetic pair breaking and, thus, to a gradual suppression of superconductivity. Pr3Ni2B2N3 exibits no long range magnetic order down to 2 K, Nd3Ni2B2N3 shows ferrimagnetic ordering below T_C = 17 K and a spin reorientation transition to a nearly antiferromagnetic state at 10 K.
In the present study, we investigate the thermodynamic properties of the Ba$_{x}$K$_{1-x}$BiO$_{3}$ (BKBO) superconductor in the under- ($x=0.5$) and over-doped ($x=0.7$) regime, within the framework of the Migdal-Eliashberg formalism. The analysis is conducted to verify that the electron-phonon pairing mechanism is responsible for the induction of the superconducting phase in the mentioned compound. In particular, we show that BKBO is characterized by the relatively high critical value of the Coulomb pseudopotential, which changes with doping level and does not follow the Morel-Anderson model. In what follows, the corresponding superconducting band gap size and related dimensionless ratio are estimated to increase with the doping, in agreement with the experimental predictions. Moreover the effective mass of electrons is found to take on high values in the entire doping and temperature region. Finally, the characteristic dimensionless ratios for the superconducting band gap, the critical magnetic field and the specific heat for the superconducting state are predicted to exceed the limits set within the Bardeen-Cooper-Schrieffer theory, suggesting pivotal role of the strong-coupling and retardation effects in the analyzed compound. Presented results supplement our previous investigations and account for the strong-coupling phonon-mediated character of the superconducting phase in BKBO at any doping level.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
