Dresden 2003 – scientific programme
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SYEC: Materials under extreme conditions
SYEC 3: Extreme Conditions (Poster Session)
SYEC 3.9: Poster
Wednesday, March 26, 2003, 13:00–19:00, P2a
High pressure investigation of the superconducting properties of the layered superconductor Y2C2I2 — •R. K. Kremer1, K. Ahn1, A. Simon1, P. Puschnig2, and C. Ambrosch-Draxl2 — 1MPI für Festkörperforschung, Stuttgart, Germany — 2Institut für Theoretische Physik, Universität Graz, Graz, Austria
The phases RE2C2X2 (X = Cl, Br, I and RE = Y, La) crystallize with layered crystal structures which contain doublelayers of close-packed metal atoms with C2 units occupying the RE octahedral voids. Such doublelayers are sandwiched by layers of halogen atoms to form X-RE-C2-RE-X slabs. The phases RE2C2X2 show superconductivity with a maximum TC of 11.6K which was achieved by adjusting the composition in the quasi-ternary phases Y2C2(X,X’)2. The variation of the TC’s with hydrostatic pressures up to ≈ 1 GPa has been found markedly different for this series, not only in magnitude but also in sign: A linear increase of 20% and 10% for 1/TC dTC / dP has been detected for La2C2Br2 and Y2C2I2, respectively, while TC decreases with pressure for Y2C2Br2 and Y2C2Br0.5I1.5 by about 3 - 4%. In this study we have reinvestigated Y2C2I2 and extended the pressure regime up to 2.2 GPa. We observe a saturation of the increase of TC with pressure above 1.5 GPa. These findings are discussed and quantitatively related to new highly resolved electronic structure calculations which reveal EF to lie in a pseudogap in the electronic density of states which gradually fills up when pressure is applied.