Department of Physics, Panjab University, Chandigarh, India

Department seminar

Date and time: 12 August 2014 (Tuesday), 2:30 pm
Venue: Seminar Hall

Title: Dramatic enhancement in superconducting properties of new BiS2 based ReO/FBiS2 superconductors (Re = La, Pr, and Nd) under hydrostic pressure

Speaker: Dr. V.P.S. Awana, National Physical Laboratory - CSIR, New Delhi

Abstract: Discovery of superconductivity in BiS2 layers of Bi4O4S3 and ReO/FBiS2 has attracted tremendous interest of both experimentalists and theoreticians from condensed matter physics community. The principal reason for it is the structural similarity of ReO/FBiS2 with the famous ReO/FFeAs pnictides high Tc superconductors. One of the issues argued is that though in HTSc cuprates and pnictides the role of 3d metal (Cu/Fe) is more important, in case of BiS2 based systems the same is played by the sp orbitals of Bi and S. Comparing the role of various Re in ReO/FFeAs and ReO/FBiS2, one finds that though Tc of (La/Pr/Nd)O0.5F0.5BiS2 is around 2.1K/3.5K/5K respectively, the same for (La/Pr/Nd)O0.8F0.2FeAs is 26K/43K/50K. It appears that chemical pressure plays an important role in superconductivity of these layered BiS2 and FeAs superconductors. We review here our efforts on synthesis and physical properties of title compounds from very beginning itself and present the new results related to impact of hydrostatic pressure on their superconductivity. The Tc of ReO/FBiS2 compounds is enhanced to fivefold for just above 1GPa external pressure, accompanied with normal state semi-metallic to metallic transition in normal state, which is thought provoking for solid state physics community.