title: Mixed dimensionality of confined conducting electrons in the surface region of SrTiO3.
abstract: Using angle-resolved photoemission spectroscopy, we show that the recently discovered surface state on SrTiO(3) consists of nondegenerate t(2g) states with different dimensional characters. While the d(xy) bands have quasi-2D dispersions with weak k(z) dependence, the lifted d(xz)/d(yz) bands show 3D dispersions that differ significantly from bulk expectations and signal that electrons associated with those orbitals permeate the near-surface region. Like their more 2D counterparts, the size and character of the d(xz)/d(yz) Fermi surface components are essentially the same for different sample preparations. Irradiating SrTiO(3) in ultrahigh vacuum is one method observed so far to induce the "universal" surface metallic state. We reveal that during this process, changes in the oxygen valence band spectral weight that coincide with the emergence of surface conductivity are disproportionate to any change in the total intensity of the O 1s core level spectrum. This signifies that the formation of the metallic surface goes beyond a straightforward chemical doping scenario and occurs in conjunction with profound changes in the initial states and/or spatial distribution of near-E(F) electrons in the surface region.
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: N C
authors.initials: NC
authors.lastname: Plumb
authors.affiliation: CNR-SPIN, Complesso Universitario Monte S. Angelo, Via Cinthia I-80126, Napoli, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Salluzzo
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Razzoli
authors.affiliation: Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Månsson
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Falub
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Krempasky
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: C E
authors.initials: CE
authors.lastname: Matt
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Chang
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schulte
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Braun
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, 81377 München, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Ebert
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, 81377 München, Germany and New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Minár
authors.affiliation: Condensed Matter Theory Group, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Delley
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: K-J
authors.initials: KJ
authors.lastname: Zhou
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Schmitt
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Shi
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Mesot
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Patthey
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Radović