<3/18(Fri),11:00>Special Talk by Dr.Sathish
1. Date and Time : 2016. 03. 18 (Fri) at 11:00
2. Place : Presentation Room on 2nd floor, Samsung Library
3. Invited speaker : Dr.Sathishi (The Seoul University)
4. Title : High Pressure Synthesis and Characterization of Non-Oxide Superconductors
High pressure research has captured growing interest in last decades due to its promising applications. Using high pressure many new superconducting and magnetic materials have been discovered so far. My research is focused mainly on different series of materials like, Transition carbide materials like MoC, Bismuth sulfide (BiS2) based layered materials Bi4O4S3 and LaOBiS2, Fe-Si based heavy fermion (LnFe3Si5) and 122 (LnFe2Si2) series of materials, Synthesis of cubic δ-MoC phases that possess useful properties for condensed matter science and possibly future technologies were carried out. A theoretical study predicted that in the case of stoichiometric MoC, if it is synthesized, superconductivity will appear at a critical temperature that is considerably higher than the critical temperatures that have thus far been achieved. Under the high-pressure and high-temperature conditions, cubic δ-MoC0.681 and δ-MoC0.746 phases were finally synthesized by heating at 6 GPa and 17 GPa, respectively. Although the stoichiometric MoC was not synthesized unfortunately under these conditions, the critical temperature of 14.3 K, which is the highest among the binary metal carbides, was evidenced to reflect the true bulk nature of δ-MoC0.746.
A new type of layered-structure material with bismuth and sulfur was claimed to be a superconductor, and it had a great impact on research as new layered superconducting material. However, the detailed properties of these materials and the cause for superconductivity were not well established. In our study, BiS2 layered Bi4O4S3 and LaOBiS2 phases were successfully synthesized in high-quality by high-pressure and high temperature technique, the crystal structure and superconductivity were investigated in detail. From the results it clearly indicated that superconductivity does not truly reflect the bulk nature of the BiS2 layered phases, regardless of the manner in which these compounds were synthesized. This conclusion contradicted the results of ongoing studies on these compounds.