J.-Q. Yan

Linear temperature dependence of resistivity and change in the Fermi surface at the pseudogap critical point of|[nbsp]|a|[nbsp]|high-Tc superconductor

Transport measurements in a high-temperature superconductor provide evidence that the so-called pseudogap phase ends at a quantum critical point located inside the superconducting dome in the phase diagram of cuprates.

LSGM-Based Solid Oxide Fuel Cell with 1.4 W/cm2 Power Density and 30 Day Long-Term Stability

A single solid oxide fuel cell (SOFC) with a La 0 . 8 Sr 0 . 2 Ga 0 . 8 3 Mg 0 . 1 7 O 2 . 8 1 5 (LSGM) electrolyte 200 μm thick with H 2 as fuel gave 1.4 W/cm 2 peak power density at 800°C. With a La 0 . 4 Ce 0 . 6 O 1 . 8 (LDC) buffer layer 20 μm thick between the electrolyte and the two electrodes, a 30-day test showed essentially no degradation of the output power. The tests demonstrated the feasibility of an SOFC operating at temperatures T < 800°C with LSGM as the electrolyte. Moreover, an LSGM electrolyte 200 μm thick with 20 μm LDC buffer layers on either side offers a convenient test bed for the exploration of new electrode materials.

Enhancement of the Nernst effect by stripe order in a high-Tc superconductor

The Nernst effect in metals is highly sensitive to two kinds of phase transition: superconductivity and density-wave order. The large, positive Nernst signal observed in hole-doped high-Tc superconductors above their transition temperature (Tc) has so far been attributed to fluctuating superconductivity. Here we report that in some of these materials the large Nernst signal is in fact the result of stripe order, a form of spin/charge modulation that causes a reconstruction of the Fermi surface. In La2-xSrxCuO4 (LSCO) doped with Nd or Eu, the onset of stripe order causes the Nernst signal to change from being small and negative to being large and positive, as revealed either by lowering the hole concentration across the quantum critical point in Nd-doped LSCO (refs 6–8) or by lowering the temperature across the ordering temperature in Eu-doped LSCO (refs 9, 10). In the second case, two separate peaks are resolved, respectively associated with the onset of stripe order at high temperature and superconductivity near Tc.