Three related topics on the periodic tables of elements

Foundations of Chemistry - A large variety of periodic tables of the chemical elements have been proposed. It was Mendeleev who proposed a periodic table based on the extensive periodic law and...     

Chiral superconducting phase transition in 3-K phase of Sr2RuO4

We have investigated the transports of micro-fabricated sample of 3-K phase superconductivity (T_c  3 K) in Sr₂RuO₄–Ru eutectic system in order to clarify the pairing symmetry. Up to now, pure Sr₂RuO₄ (T_c = 1.5 K: 1.5-K phase) is widely recognized to be a spin-triplet odd-parity superconductor. However, the enhancement mechanism of T_c up to 3 K and the pairing symmetry of the 3-K phase have not been cleared yet. By using micro fabrication technique with focused ion beam, we have succeeded to extract individual superconducting channels for the 3-K phase in which only a few pieces of Ru inclusions are contained. Multiple kink structures observed in differential resistance–current (dV/dI − I) characteristics indicate serially connected superconducting filaments in the 3-K phase. We confirm that the 3-K phase is an odd-parity superconductor similar to pure Sr₂RuO₄ from the monotonous temperature dependence of the critical currents. In addition, we observed a quite unusual hysteresis in dV/dI − I below 2 K, which suggests the internal degrees of freedom in the superconducting state: the most probably the chiral p-wave state.     

Thermal conductivity in the vicinity of the quantum critical end point in Sr3Ru2O7

Thermal conductivity of Sr3Ru2O7 was measured down to 40 mK and at magnetic fields through the quantum critical end point at Hc=7.85 T. A peak in the electrical resistivity as a function of the field was mimicked by the thermal resistivity. In the limit as T-->0 K, we find that the Wiedemann-Franz law is satisfied to within 5% at all fields, implying that there is no breakdown of the electron despite the destruction of the Fermi liquid state at quantum criticality. A significant change in disorder [from rho0(H=0 T)=2.1 to 0.5 microOmega cm] does not influence our conclusions. At finite temperatures, the temperature dependence of the Lorenz number is consistent with ferromagnetic fluctuations causing the non-Fermi liquid behavior as one would expect at a metamagnetic quantum critical end point.     

High friction from a stiff polymer using microfiber arrays

High dry friction requires intimate contact between two surfaces and is generally obtained using soft materials with an elastic modulus less than 10 MPa. We demonstrate that high-friction properties similar to rubberlike materials can also be obtained using microfiber arrays constructed from a stiff thermoplastic (polypropylene, 1 GPa). The fiber arrays have a smaller true area of contact than a rubberlike material, but polypropylene's higher interfacial shear strength provides an effective friction coefficient of greater than 5 at normal loads of 8 kPa. At the pressures tested, the fiber arrays showed more than an order of magnitude increase in shear resistance compared to the bulk material. Unlike softer materials, vertical fiber arrays of stiff polymer demonstrate no measurable adhesion on smooth surfaces due to high tensile stiffness.     

Metallic spin-liquid behavior of the geometrically frustrated Kondo lattice

Strongly frustrated magnetism of the metallic pyrochlore oxide Pr2Ir2O7 has been revealed by single crystal study. While Pr 4f moments have an antiferromagnetic RKKY interaction energy scale of /T*/ = 20 K mediated by Ir 5d-conduction electrons, no magnetic long-range order is found except for partial spin freezing at 120 mK. Instead, the Kondo effect, including a lnT dependence in the resistivity, emerges and leads to a partial screening of the moments below /T*/. Our results indicate that the underscreened moments show spin-liquid behavior below a renormalized correlation scale of 1.7 K.     

Symmetry-breaking lattice distortion in Sr₃Ru₂O₇

The electronic nematic phase of Sr?Ru?O? is investigated by high-resolution in-plane thermal expansion measurements in magnetic fields close to 8 T applied at various angles Θ off the c axis. At Θ < 10° we observe a very small (10??) lattice distortion which breaks the fourfold in-plane symmetry, resulting in nematic domains with interchanged a and b axis. At Θ ? 10° the domains are almost fully aligned and thermal expansion indicates an area-preserving lattice distortion of order 2 × 10?? which is likely related to orbital ordering. Since the system is located in the immediate vicinity of a metamagnetic quantum critical end point, the results represent the first observation of a structural relaxation driven by quantum criticality.