Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: Postersession Superconductivity: Materials - Fabrication and Properties
TT 5.37: Poster
Montag, 23. März 2009, 13:00–16:45, P1A
High pressure study of CaFe2As2 and BaFe2As2 — •William Duncan1, Oliver Welzel2, Xian-hui Chen3, Malte Grosche2, and Philipp Niklowitz1 — 1Royal Holloway, University of London, Egham, UK — 2Cavendish Laboratory, Cambridge, UK — 3Dept. of Physics, University of Science and Technology of China, Hefei, People’s Republic of China
The high pressure behaviour of the stoichiometric 1-2-2 iron arsenide compounds has been controversial. We investigate high quality stoichiometric single crystals grown from FeAs self-flux. Measurements on CaFe2As2 in a piston-cylinder pressure cell indicate a very low critical pressure of about 2 kbar for the onset of superconductivity. The pressure range in which full resistive transitions can be observed is exceedingly narrow, much less than one kbar, supporting suggestions in the literature that pressure-induced superconductivity is not a bulk phenomenon in CaFe2As2.
BaFe2As2 has been investigated up to 30 kbar in a piston-cylinder cell, and at higher pressures using anvil cell techniques, with both solid and liquid pressure media. Our data show a gradual suppression of the spin density wave/structural transition with pressure, falling below 100 K above 50 kbar. Low temperature anomalies in the resistivity below about 25 K suggest the onset of filamentary superconductivity.
We continue to explore the phase diagram of both systems to higher pressure, in order to investigate, in particular, the vicinity of the expected quantum critical point in BaFe2As2.