14.06.2012. :: Seminar Centra za fiziku cvrstog stanja i nove materijale - Cedomir Petrovic
U cetvrtak 14.06 u 12 casova u citaonici IF odrzace se seminar Centra za fiziku cvrstog stanja i nove materiijale
Stoichiometry and Superconductivity in Fe Chalcogenides
dr Cedomir Petrovic
Condensed Matter Physics
Brookhaven National Laboratory
I will outline some recent developments in iron based chalcogenide superconductors. Selected single crystal thermodynamic, transport and magnetic characterization results will be presented as well as their connection with stoichiometry and other key structural parameters that have significant influence on magnetic and superconducting states. Physica properties of binary Fe based superconductors will be focused on upper critical field behavior in high magnetic fieds [1-3]. Single crystal alloys KxFe2-ySe2-zSz offer valuable insight into the strength of electronic correlations in the normal state and structural characteristics associated with superconductivity. I will discuss the evolution of the superconducting and magnetic ground states as a function of sulfur concentration z and some noticeable changes in the average and local crystal structure associated with this [4-7]. The superconductivity persists with relatively high Tc even when electronic correlations in the normal state are greatly reduced. The results for z = 0 will be compared with other experimental techniques that probe nanoscale phase separation and degree of vacancy order [8-9]. It will be shown that local structure and population of particular Fe sites is rather important for obtaining the bulk superconducting phase. Superconducting volume fraction and homogeneity of superconducting phase is in direct competition with Fe vacancy order . References:  Phys. Rev. B 81, 094518 (2010),  Phys. Rev. B 81, 184522 (2010),  Europhys. Lett. 95, 57006 (2011),  Phys. Rev. Lett. 107, 137002 (2011)  Phys. Rev. B 83, 180503 (2011)  Phys. Rev. B 174503 (2011)  Phys. Rev. B 84, 054526 (2011)  Phys. Rev. B 83, 140505 (2011)  arXiv:1104.4941 (2011)  arXiv:1111.2597.