Development of a Rapid Temperature Scanning System for Pulsed Magnetic Fields and its Applications

AbstractAn apparatus, which scans temperature in sub-seconds for measuring the temperature dependence of the resistivity, is proposed. This apparatus contains a thermal bath and a sample platform on which a thin-film thermometer and a thin-film heater are sputtered. By thermally isolating the sample platform from surrounding parts, the sample temperature can be scanned at a high sweep rate of 200-300K/s. As a demonstration of the apparatus, the resistivity of a niobium-titanium alloy is measured in a pulsed magnetic field. In addition, as another application of the apparatus, the dielectric polarization measurement of the quantum-paraelectric material SrTiO3 is described

AC measurement of heat capacity and magnetocaloric effect for pulsed magnetic fields

International audienceA new calorimeter for measurements of the heat capacity and magnetocaloric effect of small samples in pulsed magnetic fields is discussed for the exploration of thermal and thermodynamic properties at temperatures down to 2 K. We tested the method up to 0H=50 T, but it could be extended to higher fields. For these measurements we used carefully calibrated bare-chip Cernox® and RuO2 thermometers, and we present a comparison of their performances. The monotonic temperature and magnetic field dependences of the magnetoresistance of RuO2 allow thermometry with a precision as good as 4 mK at T=2 K. To test the performance of our calorimeter, heat capacity and magnetocaloric effect for the spin-dimer compound Sr3Cr2O8 and the triangular lattice antiferromagnet RbFe MoO4 2 are presented

Correlation-driven organic 3D topological insulator with relativistic fermions

Exploring new topological phenomena and functionalities induced by strong electron correlation has been a central issue in modern condensed-matter physics. One example is a topological insulator (TI) state and its functionality driven by the Coulomb repulsion rather than a spin-orbit coupling. Here, we report a "correlation-driven" TI state realized in an organic zero-gap system $\alpha$-(BETS)$_2$I$_3$. The surface metallic state that emerges at low temperatures exhibits characteristic transport properties of a gapless Dirac semimetal, evidencing the presence of a topological surface state in this compound. Moreover, we observe a topological phase switching between the TI state and non-equilibrium Dirac semimetal state by a dc current, which is a unique functionality of a correlation-driven TI state. Our findings demonstrate that correlation-driven TIs are promising candidates not only for practical electronic devices but also as a field for discovering new topological phenomena and phases.Comment: 36 pages including 10 figure