title: Revisiting the vortex-core tunnelling spectroscopy in YBa2Cu3O7-δ.
abstract: The observation by scanning tunnelling spectroscopy of Abrikosov vortex cores in the high-temperature superconductor YBa2Cu3O7-δ (Y123) has revealed a robust pair of electron-hole symmetric states at finite subgap energy. Their interpretation remains an open question because theory predicts a different signature in the vortex cores, characterized by a strong zero-bias conductance peak. Here, we present scanning tunnelling spectroscopy data on very homogeneous Y123 at 0.4 K revealing that the subgap features do not belong to vortices: they are actually observed everywhere along the surface with high spatial and energy reproducibility, even in the absence of magnetic field. Detailed analysis and modelling show that these states remain unpaired in the superconducting phase and belong to an incoherent channel, which contributes to the tunnelling signal in parallel with the superconducting density of states.
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Jens
authors.initials: J
authors.lastname: Bruér
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Ivan
authors.initials: I
authors.lastname: Maggio-Aprile
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Nathan
authors.initials: N
authors.lastname: Jenkins
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Ristić
authors.affiliation: Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner-Strasse 8, D-85748 Garching, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Erb
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Christophe
authors.identifier: http://orcid.org/0000-0002-0787-008X
authors.initials: C
authors.lastname: Berthod
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Fischer
authors.affiliation: Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Renner