title: Absence of a proximity effect for a thin-films of a Bi2Se3 topological insulator grown on top of a Bi2Sr2CaCu2O(8+δ) cuprate superconductor.
abstract: Proximity-induced superconductivity in a 3D topological insulator represents a new avenue for observing zero-energy Majorana fermions inside vortex cores. Relatively small gaps and low transition temperatures of conventional s-wave superconductors put hard constraints on these experiments. Significantly larger gaps and higher transition temperatures in cuprate superconductors might be an attractive alternative to considerably relax these constraints, but it is not clear whether the proximity effect would be effective in heterostructures involving cuprates and topological insulators. Here, we present angle-resolved photoemission studies of thin Bi(2)Se(3) films grown in situ on optimally doped Bi(2)Sr(2)CaCu(2)O(8+δ) substrates that show the absence of proximity-induced gaps on the surfaces of Bi(2)Se(3) films as thin as a 1.5 quintuple layer. These results suggest that the superconducting proximity effect between a cuprate superconductor and a topological insulator is strongly suppressed, likely due to a very short coherence length along the c axis, incompatible crystal and pairing symmetries at the interface, small size of the topological surface state's Fermi surface, and adverse effects of a strong spin-orbit coupling in the topological material.
authors.affiliation: Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: T
authors.initials: T
authors.lastname: Yilmaz
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: I
authors.initials: I
authors.lastname: Pletikosić
authors.affiliation: National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Weber
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Sadowski
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: G D
authors.initials: GD
authors.lastname: Gu
authors.affiliation: Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Caruso
authors.affiliation: Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA.
authors.forename: B
authors.initials: B
authors.lastname: Sinkovic
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: T
authors.initials: T
authors.lastname: Valla