Truncated mass divergence in a Mott metal.

The Mott metal-insulator transition represents one of the most fundamental phenomena in condensed matter physics. Yet, basic tenets of the canonical Brinkman-Rice picture of Mott localization remain to be tested experimentally by quantum oscillation measurements that directly probe the quasiparticle Fermi surface and effective mass. By extending this technique to high pressure, we have examined the metallic state on the threshold of Mott localization in clean, undoped crystals of NiS.

Non-Fermi-Liquid Behavior of Superconducting SnH.

The chemical interaction of Sn with H by X-ray diffraction methods at pressures of 180-210 GPa is studied. A previously unknown tetrahydride SnH with a cubic structure (fcc) exhibiting superconducting properties below T  = 72 K is obtained; the formation of a high molecular C2/m-SnH superhydride and several lower hydrides, fcc SnH , and C2-Sn H , is also detected. The temperature dependence of critical current density J (T) in SnH yields the superconducting gap 2Δ(0) = 21.

Effect of Magnetic Impurities on Superconductivity in LaH.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications. On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH , encounters a serious complication because of the large upper critical magnetic field H (0), exceeding 120-160 T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH : each at% of Nd causes a decrease in T by 10-11 K, helping to control the critical parameters of this compound.

Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn.

CeRhIn provides a textbook example of quantum criticality in a heavy fermion system: Pressure suppresses local-moment antiferromagnetic (AFM) order and induces superconductivity in a dome around the associated quantum critical point (QCP) near p ≈ 23 kbar. Strong magnetic fields also suppress the AFM order at a field-induced QCP at B ≈ 50 T. In its vicinity, a nematic phase at B ≈ 28 T characterized by a large in-plane resistivity anisotropy emerges.