The quasi-two-dimensional electron gas found at the LaAlO{3}/SrTiO{3} interface offers exciting new functionalities, such as tunable superconductivity, and has been proposed as a new nanoelectronics fabrication platform. Here we lay out a new example of an electronic property arising from the interfacial breaking of inversion symmetry, namely, a large Rashba spin-orbit interaction, whose magnitude can be modulated by the application of an external electric field. By means of magnetotransport experiments we explore the evolution of the spin-orbit coupling across the phase diagram of the system. We uncover a steep rise in Rashba interaction occurring around the doping level where a quantum critical point separates the insulating and superconducting ground states of the system.

We report on a study of magnetotransport in LaAlO3/SrTiO3 interfaces characterized by mobilities of the order of several thousands cm 2 /Vs. We observe Shubnikov-de Haas oscillations that indicate a two-dimensional character of the Fermi surface. The frequency of the oscillations signals a multiple sub-bands occupation in the quantum well or a multiple valley configuration. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m * 1.45 me.An electric field applied in the back-gate geometry increases the mobility, the carrier density and the oscillation frequency.Several experimental and theoretical studies have uncovered a number of remarkable electronic properties of the interface between the complex oxides LaAlO 3 and SrTiO 3 [1][2][3][4][5]. One of the main unresolved issues pertains to the dimensionality of the conducting layer [6]. While it is now clear that, using appropriate growth and annealing conditions, a confined metallic and superconducting electron gas can be formed at such interfaces [7,8], no conclusive demonstration of two-dimensional character in the normal state has been obtained so far.X-Ray absorption spectroscopy experiments [9], as well as density functional theory calculations [10], indicate that an orbital reconstruction occurs at this interface. These studies reveal that, even at room temperature, the degeneracy of the Ti 3d t 2g levels is lifted and the first available states for the conducting electrons are generated from 3d xy orbitals, which give rise to strongly twodimensional bands and present a negligible inter-plane coupling. Moreover, the momentum quantization in the quantum well brings about a sub-bands fine structure which was calculated [10,11] but not yet confirmed experimentally. The presence of a very strong spin-orbit coupling adds further complexity to the low-energy electronic structure [12,13].The Fermi surface of two-dimensional electronic states generates clear experimental signatures in the Shubnikovde Haas (SdH) effect: for a two-dimensional electron gas (2DEG) the quantum oscillations depend only on the perpendicular component of the magnetic field. Previous studies reported quantum oscillations in LaAlO 3 /SrTiO 3−δ heterostructures characterized by a large carrier density (of the order of 10 16 cm −2 ) delocalised in the SrTiO 3 substrate [1,14]. The lack of dependence of the oscillations on the field orientation points to a three-dimensional Fermi surface consistently with previous studies in Nb-doped SrTiO 3 single crystals [15]. Very recently, quantum oscillations with two-dimensional character have been reported for Nb-doped thin films of SrTiO 3 [16]. However, in LaAlO 3 /SrTiO 3 heterostructures where the electrons are confined at the interface [6], magnetotransport studies have been carried out so far in the diffusive regime, where the scattering time is not sufficiently long to give rise to well defined Landau levels [12,[17][18][19].The requirements for observing quantum conductance oscillations are [20] ω c ...

The Materials Science beamline at the Swiss Light Source has been operational since 2001. In late 2010, the original wiggler source was replaced with a novel insertion device, which allows unprecedented access to high photon energies from an undulator installed in a medium-energy storage ring. In order to best exploit the increased brilliance of this new source, the entire front-end and optics had to be redesigned. In this work, the upgrade of the beamline is described in detail. The tone is didactic, from which it is hoped the reader can adapt the concepts and ideas to his or her needs.

Interplay of spin, charge, orbital and lattice degrees of freedom in oxide heterostructures results in a plethora of fascinating properties, which can be exploited in new generations of electronic devices with enhanced functionalities. The paradigm example is the interface between the two band insulators LaAlO3 and SrTiO3 that hosts a two-dimensional electron system. Apart from the mobile charge carriers, this system exhibits a range of intriguing properties such as field effect, superconductivity and ferromagnetism, whose fundamental origins are still debated. Here we use soft-X-ray angle-resolved photoelectron spectroscopy to penetrate through the LaAlO3 overlayer and access charge carriers at the buried interface. The experimental spectral function directly identifies the interface charge carriers as large polarons, emerging from coupling of charge and lattice degrees of freedom, and involving two phonons of different energy and thermal activity. This phenomenon fundamentally limits the carrier mobility and explains its puzzling drop at high temperatures.