Current projects

Surface 2DEG on SrTiO3(001)
Oxides surfaces and interfaces
The creation and control of novel electronic phases at the interfaces or surfaces of transition metal oxides lies at the foundation of the emergent field of oxide electronics. Using ARPES we have studied the origin and intricate electronic structure of the two-dimensional electron gas (2DEG) that occurs in the bare surfaces of SrTiO3 [Nat. Mat. 10, 114 (2011)] and KTaO3 [Phys. Rev. Lett 108, 117602(2012)].  We show that the 2DEG can be stabilized in both the (001) [Nat. Comm 5, 3414 (2014) ] and (111) [Phys. Rev. Lett. 113, 177601 (2014)] orientations and its carrier density can be tuned by alternate exposure to light and oxygen thus providing a path to study systematic variations in its electronic structure [Adv. Mat. (2015)].

Iridates
5d Iridium Oxides have an exotic insulating ground state due to the interplay between spin-orbit and weak electron-electron interactions. A clear example is the Ruddlesden-Popper series of layered perovskites (Srn+1IrnO3n+1). Sr2IrO4, isostructural to the parent compound of the copper oxides superconductors, is a pseudospin-1/2 single band Mott insulator thought to be a potential platform to engineer high-Tc superconductivity. Sr3Ir2O7, the next member of the series, is a correlated semiconductor very close to the Metal-Insulator transition. Currently we are studying by ARPES the evolution of their electronic structure as a function of electron doping and we find very different correlated metallic states for the single layer and the bilayer systems (PRL 113, 256402 (2014)).

Sr3Ir2O7 – Fermi Surface

Sr2RuO4 Fermi Surface

 

Ruthenates and Rhodates
Ruthenium and rhodium based 4d transition metal oxides show a wide range of non-trivial phases including low-dimensional Fermi liquids, spin-triplet superconductivity, Mott insulating and orbitally ordered states. The extremely high purity of ruthenate and rhodate single crystals opens a unique window to the correlated electron problem: It allows one to study an interacting fluid in a nearly perfect low-dimensional lattice, free of the complications arising from doping induced disorder. Recently we have established the low-energy electronic structure of the bilayer strontium ruthenate Sr3Ru2O7 (PRL 101, 026407 (2008)) and found strongly renormalized heavy d-electrons within an energy scale that is relevant for quantum criticality and nematicity (NJP 15 063029 (2013)).

Réalisation : Sur Mesure concept