Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0305474

Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering

A. Gurevich·S. Patnaik·V. Braccini·K. H. Kim·C. Mielke·X. Song·L. D. Cooley·S. D. Bu·D. M. Kim·J. H. Choi·L. J. Belenky·J. Giencke·M. K. Lee·W. Tian·X. Q. Pan·A. Siri·E. E. Hellstrom·C. B. Eom·D. C. Larbalestier
View original source ↗Read source document ↗Export metadata ↓

Abstract

We report a significant enhancement of the upper critical field $H_{c2}$ of different $MgB_2$ samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities $ρ$, we show a clear trend of $H_{c2}$ increase as $ρ$ increases. One particular high resistivity film had zero-temperature $H_{c2}(0)$ well above the $H_{c2}$ values of competing non-cuprate superconductors such as $Nb_3Sn$ and Nb-Ti. Our high-field transport measurements give record values $H_{c2}^\perp (0) \approx 34T$ and $H_{c2}\|(0) \approx 49 T$ for high resistivity films and $H_{c2}(0)\approx 29 T$ for untextured bulk polycrystals. The highest $H_{c2}$ film also exhibits a significant upward curvature of $H_{c2}(T)$, and temperature dependence of the anisotropy parameter $γ(T) = H_{c2}\|/ H_{c2}^\perp$ opposite to that of single crystals: $γ(T)$ decreases as the temperature decreases, from $γ(T_c) \approx 2$ to $γ(0) \approx 1.5$. This remarkable $H_{c2}$ enhancement and its anomalous temperature dependence are a consequence of the two-gap superconductivity in $MgB_2$, which offers special opportunities for further $H_{c2}$ increase by tuning of the impurity scattering by selective alloying on Mg and B sites. Our experimental results can be explained by a theory of two-gap superconductivity in the dirty limit. The very high values of $H_{c2}(T)$ observed suggest that $MgB_2$ can be made into a versatile, competitive high-field superconductor.

Explore related subjects

cond-mat.supr-con

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. Gurevich, S. Patnaik, V. Braccini, K. H. Kim, C. Mielke, X. Song, L. D. Cooley, S. D. Bu, D. M. Kim, J. H. Choi, L. J. Belenky, J. Giencke, M. K. Lee, W. Tian, X. Q. Pan, A. Siri, E. E. Hellstrom, C. B. Eom, D. C. Larbalestier. 2003-09-17. Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering. https://doi.org/10.1088/0953-2048%2F17%2F2%2F008

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Pair density waves via interband pairing --- a perspective from superfluid weight

Pair density waves (PDW) are superconducting states that exhibit a spatially modulated pairing order parameter, corresponding to Cooper pairs carrying finite center-of-mass momentum. While some recent studies have emphasized the role of quantum geometry in stabilizing PDW order in certain multiband systems, we here present a systematic investigation of an alternative, geometry-independent mechanism: PDW order driven purely by interband Cooper pairing. Using the superfluid weight (SW) as a diagnostic, we study two canonical models. The first is the classic Fulde-Ferrell model of an $s$-wave superconductor subject to a Zeeman splitting field, which realizes pure interband pairing between two rigidly shifted bands; the second is a spinless honeycomb-lattice model with nearest-neighbor $f$-wave pairing, a modified version of which was recently found to exhibit PDW instability in density-matrix renormalization-group simulations. In both models the SW receives no quantum geometric contribution at the mean-field level, yet it can be greatly suppressed or even turn negative, signaling a tendency toward pairing with spatial phase modulations. For the first model, we establish that the SW is increasingly suppressed as the Zeeman field grows, drastically turning negative upon the emergence of extensive gapless excitations, i.e., the Bogoliubov Fermi surfaces. For the honeycomb $f$-wave model, we demonstrate, both analytically and numerically, vanishing quantum-geometric SW and an invariably negative total SW. Our results thus establish the SW as a qualitative indicator of the tendency toward PDW order, and provide a microscopic rationale for the interband-pairing-driven PDW instability.

cond-mat.supr-con↗
arXiv2026

Creating functional nanostructures for vortex manipulation in superconducting Bi$_\text{2}$Sr$_\text{2}$CaCu$_\text{2}$O$_\text{8+x}$ thin films via focused He ion beam irradiation

Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (Bi-2212) is a highly anisotropic high-temperature superconductor exhibiting unique vortex dynamics due to its layered structure. Precise nanoscale patterning of ultrathin Bi-2212 films remains challenging, limiting controlled studies of vortex pinning. Here, we employ 30 keV focused helium ion beam (He-FIB) irradiation to fabricate periodic arrays of columnar defects with 100 nm spacings in optimally-doped Bi-2212 thin films, thereby creating artificial vortex pinning centers. Magnetotransport measurements reveal pronounced vortex matching effects, evidenced by minima in magnetoresistance and peaks in critical current at commensurate magnetic fields. The angular dependence of magnetoresistance and critical current scale with an effective magnetic field, indicating strong confinement of pancake vortices along irradiation-induced tracks. These findings demonstrate the efficacy of He-FIB nanopatterning in modulating the superconducting properties in Bi-2212 thin films, providing a platform for fundamental studies of vortex matter and advancing prospects for device applications based on this highly anisotropic superconductor.

cond-mat.supr-con↗
arXiv2026

Superconductivity in doped spin multimer systems

Binding energy, which quantifies pair formation, is a key factor in the emergence of superconductivity. Here, we show that even when multiple spins are complexly coupled, hole-doped systems can be mapped, in the strong-binding-energy limit, onto an effective hardcore boson model equivalent to the XXZ model, and exhibit promising signatures of superconductivity. We demonstrate this theory analytically and numerically in the double Kondo lattice model. Using the density-matrix renormalization group method, we show that a pairing state is maintained via a crossover even for parameters away from the strong-coupling regime. Additionally, we find that once binding energies are sufficiently generated, pair correlations develop similarly regardless of the details of local spin correlations. Our findings provide useful insights into the mechanism of superconductivity.

cond-mat.supr-con↗