Superconducting properties of theKxWO3tetragonal tungsten bronze and the superconducting phase diagram of the tungsten bronze family

Abstract

We report the superconducting properties of the KxWO3 tetragonal tungsten bronze. The highest superconducting transition temperature (Tc = 2.1 K) was obtained for K0.38WO3. Tc decreases linearly with increasing K content. Using the measured values for the upper critical field Hc2, and the specific heat C, we estimate the orbital critical field Hc2(0), coherence length ξ(0), Debye temperature ΘD and coupling constant λep. The magnitude of the specific heat jump at Tc suggests that the KxWO3 tetragonal tungsten bronze is a weakly-coupled superconductor. The superconducting phase diagram of the doped tungsten bronze family is presented.

The h‐SbxWO3+2x Oxygen Excess Antimony Tungsten Bronze

“…A relatively small amount of occupied states is found at the Fermi level. The resemblance of this electronic band structure to that of the conventional alkali‐based hexagonal tungsten bronzes A x WO 3 ( A =Rb, K) becomes evident upon comparison . Also the overall resistivities are in good agreement with the alkali intercalated tungsten bronzes.…”

Facet‐Independent Electric‐Field‐Induced Volume Metallization of Tungsten Trioxide Films

“…This is equivalent to 0.3 electrons per WO 3 formula unit which would need an oxygen-vacancy concentration of ≈5%, if due solely to electron donation from oxygen vacancies, i.e., a vacancy concentration more than 30 times larger than observed. This is a surprising result since it is known that chemical doped WO 3 shows metallic behavior only for large concentrations of dopants, e.g., x > 0.08 for In x WO 3 [23,27] and even x > 0.25-0.3 for Na x WO 3 , [28][29][30] i.e., the number of carriers associated with the oxygen vacancies in IL gated WO 3 is about ten times smaller than the amount of Indium needed to metallize In x WO 3 and about 30 times below that needed to metallize WO 3 by Na doping. To understand this apparent contradiction, we use X-ray photoelectron spectroscopy (XPS) and Raman studies to explore changes in electronic structure and bonding.…”

Superconducting properties of BaBi3

“…These models are widely used to calculate the µ 0 H c2 (0) for a variety of intermetallics and oxide superconductors. 19,27,28,[30][31][32]35 Also, for a oneband superconductor, the orbital upper critical field derived from the slope k = dHc2 dT | T =Tc of the H-T phase boundary at T c is an indication of clean limit µ0Hc2 k Tc = −0.73 or dirty limit µ0Hc2 k Tc = −0.69 behav-ior. BaBi 3 has the µ0Hc2 k Tc = −0.74 value, therefore BaBi 3 is a type II BCS-superconductor that is close to the clean limit.…”