Scientific Highlights

There is considerable evidence that the superconducting state of Sr₂RuO₄ breaks time reversal symmetry. In the experiments showing time reversal symmetry breaking, its onset temperature, T_TRSB, is generally found to match the critical temperature, T_c, within resolution. In combination with evidence for even parity, this result has led to consideration of a d_xz ± id_yz order parameter.

The electronic properties of transition-metal oxides with highly correlated electrons are of central importance in modern condensed-matter physics and chemistry, both for their fundamental scientific interest and for their potential for advanced electronic applications. However, the design of materials with tailored properties has been restricted by the limited understanding of their structure–property relationships, which are particularly complex in the proximity of the regime where localized electrons become gradually mobile. RENiO₃ perovskites, characterized by the presence of spontaneous metal to insulator transitions, are some of the most widely used model materials for the investigation of this region in theoretical studies. However, crucial experimental information needed to validate theoretical predictions is still lacking due to their challenging high-pressure synthesis, which has prevented to date the growth of sizable bulk single crystals with RE ≠ La, Pr, and Nd. Here we report the first successful growth of single crystals with RE = Nd, Sm, Gd, Dy, Y, Ho, Er, and Lu in sizes up to ∼75 μm, grown from molten salts in a temperature gradient under 2000 bar of oxygen gas pressure. The crystals display regular prismatic shapes with flat facets, and their crystal structures and metal–insulator and antiferromagnetic order transition temperatures are in excellent agreement with previously reported values obtained from polycrystalline samples. The availability of such crystals opens access to measurements that have hitherto been impossible to conduct. This should contribute to a better understanding of the fascinating properties of materials with highly correlated electrons and guide future efforts to engineer transition-metal oxides with tailored functional properties.

Control of interfacial reactivity at high-voltage is a key to high-energy-density Li-ion batteries. 2-aminoethyldiphenyl borate was investigated as an electrolyte additive to stabilize surface and bulk of both NCM851005 and graphite in the cell with upper cut-off voltage of 4.4 V vs Li+/Li. AEDB almost completely eliminated the “cross-talk” in the cell, by significantly reducing metal leaching from the cathode, preventing their deposition at the anode, and further electrolyte decomposition.

CeRh₂As₂, a nonsymmorphic heavy fermion material, was recently reported to host a remarkable temperature versus z-axis magnetic-field phase diagram with two superconducting phases. In this material, the two inequivalent Ce sites per unit cell, related by inversion symmetry, introduce a sublattice structure corresponding to an extra internal degree of freedom. In this work, we propose a classification of the possible superconducting states in CeRh₂As₂ from the two Ce-sites' perspective.

Schematic representation of the method used to grow RENiO₃ nickelate single crystals covering the full 4f series and Y. This novel procedure, based on the use of moderate oxygen gas pressures (2000 bar), solvothermal growth in a temperature gradient, and highly reactive eutectic salt mixtures as fluxes, yields prismatic-shaped crystals with flat facets and sizes up to ∼75 μm.