Formation of tungsten carbide by focused ion beam process: A route to high magnetic field resilient patterned superconducting nanostructures

Abstract

A scale for magnetic field resilience of a superconductor is set by the paramagnetic limit. Comparing the condensation energy of the Bardeen-Cooper-Schrieffer (BCS) singlet ground state with the paramagnetically polarised state suggests that for an applied field ${\mu }_{0}H>1.8T_c$ (in SI), singlet pairing is not energetically favourable. Materials exceeding or approaching this limit are interesting from fundamental and technological perspectives. This may be a potential indicator of triplet superconductivity, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing and other mechanisms involving topological aspects of surface states, and also allow Cooper pair injection at high magnetic fields. We have analysed the microscopic composition of such a material arising from an unexpected source. A microjet of an organo-metallic gas, $\mathrm{W}[(\mathrm{CO}{)}_6]$ can be decomposed by gallium ion-beam, leaving behind a track of complex residue of gallium, tungsten and carbon with remarkable superconducting properties, like an upper critical field, $H_{c2}>10\mathrm{T}$, above its paramagnetic limit. We carried out Atomic probe tomography to establish the formation of nano-crystalline tungsten carbide (WC) in the tracks and the absence of free tungsten. Supporting calculations show for Ga distributed on the surface of WC, its s,p-orbitals enhance the density of states near the Fermi energy. The observed variation of $H_{c2}(T)$ does not show features typical of enhancement of critical field due to granularity. Our observations may be significant in the context of some recent theoretical calculation of the band structure of WC and experimental observation of superconductivity in WC-metal interface.

arXiv comment6 pages, 3 figures, 59 References

References in corpus (19)

• Superconductivity in CuxBi2Se3 and its implications for pairing in the undoped topological insulator
• Two Dimensional Ising Superconductivity in Gated MoS${}_2$
• Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors
• Inducing Superconducting Correlation in Quantum Hall Edge States
• Unconventional Superconductivity at Mesoscopic Point-contacts on the 3-Dimensional Dirac Semi-metal Cd${}_3$As${}_2$
• Rotational Symmetry Breaking in a Trigonal superconductor Nb-doped Bi2Se3
• Focused-ion-beam-induced deposition of superconducting nanowires
• Three-component fermions with surface Fermi arcs in topological semimetal tungsten carbide
• Ultra-fast vortex motion in dirty Nb-C superconductor with a close-to-perfect edge barrier
• Nanoscale superconducting properties of amorphous W-based deposits grown with focused-ion-beam
• Superconducting nanowires by electron-beam-induced deposition
• Superconductivity with High Upper Critical Field in the Cubic Centrosymmetric $\eta$-Carbide Nb${}_4$Rh${}_2$C${}_{1-\delta }$
• Superconductivity Induced at a Point Contact on the Topological Semimetal Tungsten Carbide
• Superconductivity in nanocrystalline tungsten thin films growth by sputtering in a nitrogen-argon mixture
• Evidence of Interfacial Topological Superconductivity on the Topological Semimetal Tungsten Carbide Induced by Metal Deposition
• Effect of granularity on the insulator-superconductor transition in ultrathin Bi films
• Chiral flat band superconductivity from symmetry-protected three-band crossings
• Critical currents and vortex-unbinding transitions in quench-condensed ultrathin films of Bismuth and Tin
• Possible robust insulator-superconductor transition on solid inert gas and other substrates