[en] The authors have investigated the transport properties, resistivity and Hall effect, in a series of underdoped GdBa₂Cu₃O_x thin films grown by off-axis magnetron sputtering. They find a systematic correlation between the critical temperature Tc and the inverse Hall constant R_H^-1, related, in simple models, to the carrier concentration n. The experimental thin film Tc(n) data are in good agreement with the temperature-doping phase diagram obtained for YBa₂Cu₃O_x single crystals. By measuring the activation energies in the liquid vortex phase, and by using a 2-dimensional model for vortex dynamics, they have extracted the penetration depth of these samples, and studied the relation between the carrier concentration and the superfluid density to probe the role of phase fluctuations on superconductivity

[en] Perovskite SrRuO₃ films are promising candidates as metallic electrodes in high-permittivity (high k) capacitors and possibly in fully epitaxial CMOS stacks. The thermal stability of SrRuO₃ during forming-gas (FG) anneal is an important requirement and is investigated here by in situ X-ray diffraction (XRD) and electrical resistivity measurements. A weak and smooth increase of the resistivity is observed above 300 deg. C and is attributed to the effect of hydrogen diffusion. It is followed by a sharp transition at 500 deg. C into a highly resistive state due to the decomposition of the SrRuO₃. We found that the addition of about 1% O₂ in the FG prevents both the onset of resistivity at 300 deg. C and the decomposition of the oxide

[en] Physical and structural phenomena originating from polar discontinuities have generated enormous activity. In the last ten years, the oxide interface between polar $\text{LaAl}{\text{O}}_3$ and non-polar $\text{SrTi}{\text{O}}_3$, both band insulators, has attracted particular interest, as it hosts an electron liquid with remarkable properties: it superconducts, has a sizeable spin–orbit interaction and its properties are tunable by an electric field. The profile of the carrier density at the interface and the exact band structure are properties strongly linked and still objects of debate. Here we review the experimental findings on the origin and the extension of the electron liquid and discuss the theoretical models developed to describe the charge profile and the band structure. We also introduce a model to account for the effect of interface disorder which could modify the charge distribution. (topical review)

[en] We report on the structural characterization of LaAlO₃/SrTiO₃ interfaces and on their transport properties. LaAlO₃ films were prepared using pulsed laser deposition onto TiO₂ terminated (001) SrTiO₃ substrates inducing a metallic conduction at the interface. Resistance and Hall effect measurements reveal a sheet carrier density between 0.4 and 1.2 x 10¹⁴ electrons cm^-2 at room temperature and a mobility of ∼300 cm² V^-1 s^-1 at low temperatures. A transition to a superconducting state is observed at a temperature of ∼200 mK. The superconducting characteristics display signatures of 2D superconductivity.

[en] We present a brief review of the role of interfacial physics in ferroelectric oxides, with an emphasis on the importance of boundary conditions that determine the properties of very thin ferroelectric films and superlattices. As well as discussing the screening problem, and the role of strain and electrostatics in ferroelectrics, we highlight some of the possibilities in fine period superlattices where the high density of interfaces can lead to new and potentially useful phenomena

[en] We report a detailed analysis of magneto-transport properties of top- and back-gated LaAlO₃/SrTiO₃ heterostructures. Efficient modulation in magneto-resistance, carrier density, and mobility of the two-dimensional electron liquid present at the interface is achieved by sweeping top and back gate voltages. Analyzing those changes with respect to the carrier density tuning, we observe that the back gate strongly modifies the electron mobility while the top gate mainly varies the carrier density. The evolution of the spin-orbit interaction is also followed as a function of top and back gating

[en] We have studied the electronic properties of the 2D electron liquid present at the LaAlO₃/SrTiO₃ interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650 °C exhibit the highest low temperature mobility (≈10 000 cm² V⁻¹ s⁻¹) and the lowest sheet carrier density (≈5×10¹² cm⁻²). These samples show metallic behavior and Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at higher temperatures (800–900 °C) display carrier densities in the range of ≈2−5×10¹³ cm⁻² and mobilities of ≈1000 cm² V⁻¹ s⁻¹ at 4 K. Reducing their carrier density by field effect to 8×10¹² cm⁻² lowers their mobilities to ≈50 cm² V⁻¹ s⁻¹ bringing the conductance to the weak-localization regime

[en] Full text: The quasi-two-dimensional electron gas found at the LaAlO₃/SrTiO₃ interface offers exciting new functionalities, such as electric field tunable superconductivity. By means of transport measurements in field-effect devices, previous experiments revealed that a strong Rashba spin-orbit coupling is developing as the critical temperature is increasing. In this work, we explore the evolution of the magneto-conductance across the phase diagram for magnetic fields applied in-plane and out-of-plane. A strong sensitivity of the electron gas properties to the strength and orientation of the magnetic field (also with respect to the current direction), temperature, and doping is observed. In the normal state, these measurements allow the different contributions (orbital, electron-electron interaction, Zeeman) to the magneto-conductance to be revealed. In the superconducting state, a transition from an insulating to a metallic state is uncovered. (author)

[en] Full text: At interfaces between complex oxides, electronic systems with unusual properties can be generated. A striking example is the interface between LaAlO₃ and SrTiO₃, two good band insulating perovskites, which was found in 2004 to be conducting with a high mobility. The ground state of this system is a 2D superconducting condensate with a critical temperature of about 200 mK. This electron gas with low electronic density, typically 5x10¹³ electrons/cm², naturally sandwiched between two insulators, is ideal for performing electric field effect experiments allowing the carrier density to be tuned. Such an approach revealed the sensitivity of the normal and superconducting states to the carrier density. In particular, the electric field allows the tuning of the critical temperature between 200 mK and 0 K and thus the on-off switching of superconductivity. The system phase diagram reveals a superconducting pocket with an underdoped and an overdoped regime. A large, interfacially generated, tunable spin-orbit coupling and a remarkable correlation between the spin-orbit coupling strength and the system phase diagram are other hallmarks of this fascinating system. Recent developments allow high mobility samples to be grown. In such samples, resistance measurements display Shubnikov de Haas oscillations pointing to 2D electronic states. (author)

[en] Within the last twenty years, the status of the spin–orbit interaction has evolved from that of a simple atomic contribution to a key effect that modifies the electronic band structure of materials. It is regarded as one of the basic ingredients for spintronics, locking together charge and spin degrees of freedom and recently it is instrumental in promoting a new class of compounds, the topological insulators. In this review, we present the current status of the research on the spin–orbit coupling in transition metal oxides, discussing the case of two semiconducting compounds, and , and the properties of surface and interfaces based on these. We conclude with the investigation of topological effects predicted to occur in different complex oxides. (key issues review)