Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery of Superconductivity in (Ba,K)SbO$_{3}$
59
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Superconducting bismuthates (Ba,K)BiO$_{3}$ (BKBO) constitute an interesting class of superconductors in that superconductivity with a remarkably high $T_mathrm{c}$ of 30 K arises in proximity to charge density wave (CDW) order. Prior understanding on the driving mechanism of the CDW and superconductivity emphasizes the role of either bismuth (negative $U$ model) or oxygen ions (ligand hole model). While holes in BKBO presumably reside on oxygen owing to their negative charge transfer energy, so far there has been no other comparative material studied. Here, we introduce (Ba,K)SbO$_{3}$ (BKSO) in which the Sb 5$s$ orbital energy is higher than that of the Bi 6$s$ orbitals enabling tuning of the charge transfer energy from negative to slightly positive. The parent compound BaSbO$_{3-delta}$ shows a larger CDW gap compared to the undoped bismuthate BaBiO$_{3}$. As the CDW order is suppressed via potassium substitution up to 65 %, superconductivity emerges, rising up to $T_mathrm{c}$ = 15 K. This value is lower than the maximum $T_mathrm{c}$ of BKBO, but higher by more than a factor of two at comparable potassium concentrations. The discovery of an enhanced CDW gap and superconductivity in BKSO indicates that the sign of the charge transfer energy may not be crucial, but instead strong metal-oxygen covalency plays the essential role in constituting a CDW and high-$T_mathrm{c}$ superconductivity in the main-group perovskite oxides.
rate research
Read More
In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional superconductors like niobium or lead, the normal state is a Fermi liquid with a well-defined Fermi surface and well-defined quasipartcles along the Fermi surface. Superconductivity is realized in this case by the Fermi surface instability in the superconducting state and the formation and condensation of the electron pairs (Cooper pairing). The high temperature cuprate superconductors, on the other hand, represent another extreme case that superconductivity can be realized in the underdoped region where there is neither well-defined Fermi surface due to the pseudogap formation nor quasiparticles near the antinodal regions in the normal state. Here we report a novel scenario that superconductivity is realized in a system with well-defined Fermi surface but without quasiparticles along the Fermi surface in the normal state. High resolution laser-based angle-resolved photoemission measurements have been performed on an optimally-doped iron-based superconductor (Ba$_{0.6}$K$_{0.4}$)Fe$_2$As$_2$. We find that, while sharp superconducting coherence peaks emerge in the superconducting state on the hole-like Fermi surface sheets, no quasiparticle peak is present in the normal state. Its electronic behaviours deviate strongly from a Fermi liquid system. The superconducting gap of such a system exhibits an unusual temperature dependence that it is nearly a constant in the superconducting state and abruptly closes at T$_c$. These observations have provided a new platform to study unconventional superconductivity in a non-Fermi liquid system.
Combining experiments and ab initio models we report on $rm SrPt_4Ge_{12}$ and $rm BaPt_4Ge_{12}$ as members of a novel class of superconducting skutterudites, where Sr or Ba atoms stabilize a framework entirely formed by Ge-atoms. Below $T_c=5.35$ K, and 5.10 K for $rm BaPt_4Ge_{12}$ and $rm SrPt_4Ge_{12}$, respectively, electron-phonon coupled superconductivity emerges, ascribed to intrinsic features of the Pt-Ge framework, where Ge-$p$ states dominate the electronic structure at the Fermi energy.
High pressure electrical resistance and x-ray diffraction measurements have been performed on ruthenium-doped Ba(Fe0.9Ru0.1)2As2, up to pressures of 32 GPa and down to temperatures of 10 K, using designer diamond anvils under quasi-hydrostatic conditions. At 3.9 GPa, there is an evidence of pressure-induced superconductivity with Tc onset of 24 K and zero resistance at Tc zero of ~14.5 K. The superconducting transition temperature reaches maximum at ~5.5 GPa and then decreases gradually with increase in pressure before completely disappearing above 11.5 GPa. Upon increasing pressure at 200 K, an isostructural phase transition from a tetragonal (I4/mmm) phase to a collapsed tetragonal phase is observed at 14 GPa and the collapsed phase persists up to at least 30 GPa. The changes in the unit cell dimensions are highly anisotropic across the phase transition and are qualitatively similar to those observed in undoped BaFe2As2 parent.
We report superconductivity in as synthesized Nb2PdSe5, which is similar to recently discovered Nb2PdS5 compound having very high upper critical field, clearly above the Pauli paramagnetic limit [Sci. Rep. 3, 1446 (2013)]. A bulk polycrystalline Nb2PdSe5 sample is synthesized by solid state reaction route in phase pure structure. The structural characterization has been done by X ray diffraction, followed by Rietveld refinements, which revealed that Nb2PdSe5 sample is crystallized in monoclinic structure with in space group C2/m. Structural analysis revealed the formation of sharing of one dimensional PdSe2 chains. Electrical and magnetic measurements confirmed superconductivity in Nb2PdSe5 compound at 5.5K. Detailed magneto-resistance results, exhibited the value of upper critical field to be around 8.2Tesla. The estimated Hc2(0) is within Pauli Paramagnetic limit, which is unlike the Nb2PdS5.
The calcium superhydrides are synthesized at high pressure of 180 GPa and 1000 degree high temperatures. Superconductivity with Tc onset about 210 K is realized in thus obtained hydrogen rich calcium compounds at high pressure. The critical magnetic field Hc2(T) is estimated to around 166 T in the Ginzburg Landau model.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
