caa a22 4500 53009892X 20181217030327.0 cr unu---uuuuu 181026e20160524xx s 000 0 eng 10.3929/ethz-b-000117010 doi 10.1038/srep26394 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/117010 Fermi-Surface Topological Phase Transition and Horizontal Order-Parameter Nodes in CaFe2As2 Under Pressure [Elektronische Daten] [Renato S. Gonnelli, Dario Daghero, Mauro Tortello, Giovanni A. Ummarino, Zbigniew Bukowski, Janusz Karpinski, Patrick G. Reuvekamp, Reinhard K. Kremer, Gianni Profeta, K. Suzuki, Kazuhiko Kuroki] Sci Rep Open access ethresearch Iron-based compounds (IBS) display a surprising variety of superconducting properties that seems to arise from the strong sensitivity of these systems to tiny details of the lattice structure. In this respect, systems that become superconducting under pressure, like CaFe2As2, are of particular interest. Here we report on the first directional point-contact Andreev-reflection spectroscopy (PCARS) measurements on CaFe2As2 crystals under quasi-hydrostatic pressure, and on the interpretation of the results using a 3D model for Andreev reflection combined with ab-initio calculations of the Fermi surface (within the density functional theory) and of the order parameter symmetry (within a random-phase-approximation approach in a ten-orbital model). The almost perfect agreement between PCARS results at different pressures and theoretical predictions highlights the intimate connection between the changes in the lattice structure, a topological transition in the holelike Fermi surface sheet, and the emergence on the same sheet of an order parameter with a horizontal node line. Creative Commons Attribution 4.0 International http://creativecommons.org/licenses/by/4.0 ethresearch Electronic properties and materials ethresearch Superconducting properties and materials ethresearch Gonnelli Renato S. joint author Daghero Dario joint author Tortello Mauro joint author Ummarino Giovanni A. joint author Bukowski Zbigniew joint author Karpinski Janusz joint author Reuvekamp Patrick G. joint author Kremer Reinhard K. joint author Profeta Gianni joint author Suzuki K. joint author Kuroki Kazuhiko joint author Scientific Reports London : Nature Publishing Group 6, p. 26394 2045-2322 http://hdl.handle.net/20.500.11850/117010 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/117010 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 700 1- Gonnelli Renato S. joint author ETHRESEARCH 700 1- Daghero Dario joint author ETHRESEARCH 700 1- Tortello Mauro joint author ETHRESEARCH 700 1- Ummarino Giovanni A. joint author ETHRESEARCH 700 1- Bukowski Zbigniew joint author ETHRESEARCH 700 1- Karpinski Janusz joint author ETHRESEARCH 700 1- Reuvekamp Patrick G. joint author ETHRESEARCH 700 1- Kremer Reinhard K. joint author ETHRESEARCH 700 1- Profeta Gianni joint author ETHRESEARCH 700 1- Suzuki K. joint author ETHRESEARCH 700 1- Kuroki Kazuhiko joint author ETHRESEARCH 773 0- Scientific Reports London : Nature Publishing Group 6, p. 26394 2045-2322 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access