Probing -wave superconductivity in UTe via point-contact junctions.

Uranium ditelluride (UTe) is the strongest contender to date for a -wave superconductor in bulk form. Here we perform a spectroscopic study of the ambient pressure superconducting phase of UTe, measuring conductance through point-contact junctions formed by metallic contacts on different crystalline facets down to 250 mK and up to 18 T. Fitting a range of qualitatively varying spectra with a Blonder-Tinkham-Klapwijk (BTK) model for -wave pairing, we can extract gap amplitude and interface barrier strength for each junction.

Pressure-Induced Exciton Formation and Superconductivity in Platinum-Based Mineral Sperrylite.

We report a comprehensive study of Sperrylite (PtAs), the main platinum source in natural minerals, as a function of applied pressures up to 150 GPa. While no structural phase transition is detected from pressure-dependent X-ray measurements, the unit cell volume shrinks monotonically with pressure following the third-order Birch-Murnaghan equation of state. The mildly semiconducting behavior found in pure synthesized crystals at ambient pressures becomes more insulating upon increasing the applied pressure before metalizing at higher pressures, giving way to the appearance of an abrupt decrease in resistance near 3 K at pressures above 92 GPa consistent with the onset of a superconducing phase.

Orphan high field superconductivity in non-superconducting uranium ditelluride.

Reentrant superconductivity is an uncommon phenomenon in which the destructive effects of magnetic field on superconductivity are mitigated, allowing a zero-resistance state to survive under conditions that would otherwise destroy it. Typically, the reentrant superconducting region derives from a zero-field parent superconducting phase. Here, we show that in UTe crystals extreme applied magnetic fields give rise to an unprecedented high-field superconductor that lacks a zero-field antecedent.

Resonant Ultrasound Spectroscopy for Irregularly Shaped Samples and Its Application to Uranium Ditelluride.

Resonant ultrasound spectroscopy (RUS) is a powerful technique for measuring the full elastic tensor of a given material in a single experiment. Previously, this technique was practically limited to regularly shaped samples such as rectangular parallelepipeds, spheres, and cylinders [W. M.

Potential Lifshitz transition at optimal substitution in nematic pnictide BaSrNiAs.

BaNiAs is a structural analog of the pnictide superconductor BaFeAs, which, like the iron-based superconductors, hosts a variety of ordered phases including charge density waves (CDWs), electronic nematicity, and superconductivity. Upon isovalent Sr substitution on the Ba site, the charge and nematic orders are suppressed, followed by a sixfold enhancement of the superconducting transition temperature (). To understand the mechanisms responsible for enhancement of , we present high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements of the BaSrNiAs series, which agree well with our density functional theory (DFT) calculations throughout the substitution range.