title: Two-dimensional electron gas with six-fold symmetry at the (111) surface of KTaO3.
abstract: Two-dimensional electron gases (2DEGs) at transition-metal oxide (TMO) interfaces, and boundary states in topological insulators, are being intensively investigated. The former system harbors superconductivity, large magneto-resistance, and ferromagnetism. In the latter, honeycomb-lattice geometry plus bulk spin-orbit interactions lead to topologically protected spin-polarized bands. 2DEGs in TMOs with a honeycomb-like structure could yield new states of matter, but they had not been experimentally realized, yet. We successfully created a 2DEG at the (111) surface of KTaO3, a strong insulator with large spin-orbit coupling. Its confined states form a network of weakly-dispersing electronic gutters with 6-fold symmetry, a topology novel to all known oxide-based 2DEGs. If those pertain to just one Ta-(111) bilayer, model calculations predict that it can be a topological metal. Our findings demonstrate that completely new electronic states, with symmetries not realized in the bulk, can be tailored in oxide surfaces, promising for TMO-based devices.
authors.affiliation: CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Bareille
authors.affiliation: CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Fortuna
authors.affiliation: 1] CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France [2] Universität Würzburg, Experimentelle Physik VII, Am Hubland, 97074 Würzburg, Germany.
authors.forename: T C
authors.initials: TC
authors.lastname: Rödel
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France.
authors.forename: F
authors.initials: F
authors.lastname: Bertran
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud and CNRS, Bâtiment 510, 91405 Orsay, France.
authors.forename: M
authors.initials: M
authors.lastname: Gabay
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud and CNRS, Bâtiment 510, 91405 Orsay, France.
authors.forename: O Hijano
authors.initials: OH
authors.lastname: Cubelos
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France.
authors.forename: A
authors.initials: A
authors.lastname: Taleb-Ibrahimi
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Le Fèvre
authors.affiliation: Unité Mixte de Physique CNRS/Thales, Campus de l'Ecole Polytechnique, 1 Av. A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: M
authors.initials: M
authors.lastname: Bibes
authors.affiliation: Unité Mixte de Physique CNRS/Thales, Campus de l'Ecole Polytechnique, 1 Av. A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay, France.
authors.forename: A
authors.initials: A
authors.lastname: Barthélémy
authors.affiliation: Institut d'Electronique Fondamentale, Université Paris-Sud and CNRS, Bâtiment 220, 91405 Orsay, France.
authors.forename: T
authors.initials: T
authors.lastname: Maroutian
authors.affiliation: Institut d'Electronique Fondamentale, Université Paris-Sud and CNRS, Bâtiment 220, 91405 Orsay, France.
authors.forename: P
authors.initials: P
authors.lastname: Lecoeur
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud and CNRS, Bâtiment 510, 91405 Orsay, France.
authors.forename: M J
authors.initials: MJ
authors.lastname: Rozenberg
authors.affiliation: CSNSM, Université Paris-Sud and CNRS/IN2P3, Bâtiments 104 et 108, 91405 Orsay cedex, France.
authors.forename: A F
authors.initials: AF
authors.lastname: Santander-Syro