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ABSTRACT: We describe the transport properties of mesoscopic devices based on the two
dimensional electron gas (2DEG) present at the LaAlO$_3$/SrTiO$_3$ interface.
Bridges with lateral dimensions down to 500~nm were realized using electron
beam lithography. Their detailed characterization shows that processing and
confinement do not alter the transport parameters of the 2DEG. The devices
exhibit superconducting behavior tunable by electric field effect. In the
normal state, we measured universal conductance fluctuations, signature of
phase-coherent transport in small structures. The achievement of reliable
lateral confinement of the 2DEG opens the way to the realization of quantum
electronic devices at the LaAlO$_3$/SrTiO$_3$ interface.
06/2013;
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ABSTRACT: We report measurements of the normal state in-plane magnetoconductance in
gated LaAlO$_3$-SrTiO$_3$ samples. As the orientation of the magnetic field
changes within the plane of the interface, the signal displays periodic
oscillations with respect to the angle between the field and the direction of
the current. We show that in the underdoped to optimally doped range, a Fermi
surface reconstruction takes place due to the Rashba spin-orbit term and that
the oscillations are due to a magnetic field induced opening and closing of a
gap at the $\Gamma$ point for those Ti out-of-plane orbitals having their band
minimum close to the Fermi energy of the system.
03/2012;
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C Cancellieri,
D Fontaine,
S Gariglio,
N Reyren, A D Caviglia,
A Fête,
S J Leake,
S A Pauli,
P R Willmott,
M Stengel,
Ph Ghosez,
J-M Triscone
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ABSTRACT: We present a direct comparison between experimental data and ab initio calculations for the electrostrictive effect in the polar LaAlO(3) layer grown on SrTiO(3) substrates. From the structural data, a complete screening of the LaAlO(3) dipole field is observed for film thicknesses between 6 and 20 uc. For thinner films, an expansion of the c axis of 2% matching the theoretical predictions for an electrostrictive effect is observed experimentally.
Physical Review Letters 07/2011; 107(5):056102. · 7.37 Impact Factor
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C. Cancellieri,
D. Fontaine,
S. Gariglio,
N. Reyren, A. D. Caviglia,
A. Fête,
S. J. Leake,
S. A. Pauli,
P. R. Willmott,
M. Stengel,
Ph. Ghosez,
J.-M. Triscone
[show abstract]
[hide abstract]
ABSTRACT: We present a direct comparison between experimental data and ab initio calculations for the electrostrictive effect in the polar LaAlO3 layer grown on SrTiO3 substrates. From the structural data, a complete screening of the LaAlO3 dipole field is observed for film thicknesses between 6 and 20 uc. For thinner films, an expansion of the c axis of 2% matching the theoretical predictions for an electrostrictive effect is observed experimentally.
Physical Review Letters 07/2011; 107(5):056102. · 7.37 Impact Factor
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ABSTRACT: We report on a study of magnetotransport in LaAlO3 /SrTiO3 interfaces characterized by mobilities of the order of several thousands cm2/V s. We observe Shubnikov-de Haas oscillations whose period depends only on the perpendicular component of the magnetic field. This observation directly indicates the formation of a two-dimensional electron gas originating from quantum confinement at the interface. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m* ≃ 1.45 m(e). An electric field applied in the back-gate geometry increases the mobility, the carrier density, and the oscillation frequency.
Physical Review Letters 12/2010; 105(23):236802. · 7.37 Impact Factor
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ABSTRACT: The effects of oxygen pressure during the growth of LaAlO3 on (001) SrTiO3, and of post-deposition annealing were investigated. While little influence on the structure was observed, the transport properties were found to depend on both growth pressure and annealing. For LaAlO3 layer thicknesses between 5 and 10 unit cells and growth pressures between 10− 4 and 10−2 mbar, the LaAlO3/SrTiO3 interfaces displayed similar metallic behavior with a sharp transition to a superconducting state. At an oxygen pressure of 10− 6 mbar oxygen vacancies were clearly introduced and extended deep into the SrTiO3 crystal. These vacancies could be removed by post-deposition annealing in 0.2 bar of O2 at ~530 °C. At a growth pressure of 10− 4 mbar, the electronic properties of samples with ultra-thin LaAlO3 layers (2 to 3 unit cells thick) were found to depend markedly on the post-annealing step.
EPL (Europhysics Letters) 07/2010; 91(1):17004. · 2.17 Impact Factor
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R. Jany,
M. Breitschaft,
G. Hammerl,
A. Horsche,
C. Richter,
S. Paetel,
J. Mannhart,
N. Stucki,
N. Reyren,
S. Gariglio,
P. Zubko, A. D. Caviglia,
J.-M. Triscone
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ABSTRACT: Using the metal-insulator transition that takes place as a function of carrier density at the LaAlO <sub>3</sub>– SrTiO <sub>3</sub> interface, oxide diodes have been fabricated with room-temperature breakdown voltages of up to 200 V. With applied voltage, the capacitance of the diodes changes by a factor of 150. The diodes are robust and operate at temperatures up to 270 C.
Applied Physics Letters 06/2010; · 3.84 Impact Factor
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R. Jany,
M. Breitschaft,
G. Hammerl,
A. Horsche,
C. Richter,
S. Paetel,
J. Mannhart,
N. Stucki,
N Reyren,
S. Gariglio,
P. Zubko, A D Caviglia,
J-M Triscone
[show abstract]
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ABSTRACT: Using the metal-insulator transition that takes place as a function of carrier density at the LaAlO$_3$-SrTiO$_3$ interface, oxide diodes have been fabricated with room-temperature breakdown voltages of up to 200 V. With applied voltage, the capacitance of the diodes changes by a factor of 150. The diodes are robust and operate at temperatures up to 270 C.
05/2010;
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ABSTRACT: 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.
Physical Review Letters 03/2010; 104(12):126803. · 7.37 Impact Factor
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ABSTRACT: The observation of metallic behavior at the interface between insulating oxides has triggered worldwide efforts to shed light on the physics of these systems and clarify some still open issues, among which the dimensional character of the conducting system. In order to address this issue, we measure electrical transport (Seebeck effect, Hall effect and conductivity) in LaAlO_{3}/SrTiO_{3} interfaces and, for comparison, in a doped SrTiO_{3} bulk single crystal. In these experiments, the carrier concentration is tuned, using the field effect in a back gate geometry. The combined analysis of all experimental data at 77 K indicates that the thickness of the conducting layer is ~7 nm and that the Seebeck effect data are well described by a two-dimensional (2D) density of states. We find that the back gate voltage is effective in varying not only the charge density, but also the thickness of the conducting layer, which is found to change by a factor of ~2, using an electric field between -4 and +4MV/m at 77K. No enhancement of the Seebeck effect due to the electronic confinement and no evidence for two-dimensional quantization steps are observed at the interfaces. Comment: 15 pages, 5 figures
02/2010;
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ABSTRACT: Recently superconductivity at the interface between the insulators LaAlO3 and SrTiO3 has been tuned with the electric field effect to an unprecedented range of transition temperatures. Here we perform a detailed finite size scaling analysis to explore the compatibility of the phase transition line with Berezinskii-Kosterlitz-Thouless (BKT) behavior and a 2D-quantum phase(QP)-transition. In an intermediate regime, limited by a gate voltage dependent limiting length, we uncover remarkable consistency with a BKT-critical line ending at a metallic quantum critical point, separating a weakly localized insulator from the superconducting phase. Our estimates for the critical exponents of the 2D-QP-transition, z=1 and nu=0.66, suggest that it belongs to the 3D-xy universality class.
05/2009;
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ABSTRACT: We report on the structural characterization of LaAlO(3)/SrTiO(3) interfaces and on their transport properties. LaAlO(3) films were prepared using pulsed laser deposition onto TiO(2) terminated (001) SrTiO(3) substrates inducing a metallic conduction at the interface. Resistance and Hall effect measurements reveal a sheet carrier density between 0.4 and 1.2 × 10(14) electrons cm(-2) at room temperature and a mobility of ∼300 cm(2) 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.
Journal of Physics Condensed Matter 04/2009; 21(16):164213. · 2.55 Impact Factor
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ABSTRACT: The superconducting transport properties of the conducting LaAlO <sub>3</sub>/ SrTiO <sub>3</sub> interface have been investigated in perpendicular and parallel magnetic fields. A large anisotropy in the transport properties is measured and the two-dimensional nature of the superconducting gas is confirmed. Analyses of the resistance versus temperature and magnetic field, as well as of the correlation length as a function of the magnetic field close to the superconducting critical temperature (about 200 mK), yield an estimate of ∼10 nm for the superconducting layer thickness.
Applied Physics Letters 04/2009; · 3.84 Impact Factor
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ABSTRACT: 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 × 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.
Journal of Physics Condensed Matter 03/2009; 21(16):164213. · 2.55 Impact Factor
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ABSTRACT: We report experimental investigations of the effects of microstructural defects and of disorder on the properties of 2D electron gases at oxide interfaces. The cross section for scattering of electrons at dislocations in LaAlO(3)/SrTiO(3) interfaces has been measured and found to equal approximately 5 nm. Our experiments reveal that the transport properties of these electron gases are strongly influenced by scattering at dislocation cores.
Physical Review Letters 02/2009; 102(4):046809. · 7.37 Impact Factor
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ABSTRACT: Interfaces between complex oxides are emerging as one of the most interesting systems in condensed matter physics. In this special setting, in which translational symmetry is artificially broken, a variety of new and unusual electronic phases can be promoted. Theoretical studies predict complex phase diagrams and suggest the key role of the charge carrier density in determining the systems' ground states. A particularly fascinating system is the conducting interface between the band insulators LaAlO(3) and SrTiO(3) (ref. 3). Recently two possible ground states have been experimentally identified: a magnetic state and a two-dimensional superconducting condensate. Here we use the electric field effect to explore the phase diagram of the system. The electrostatic tuning of the carrier density allows an on/off switching of superconductivity and drives a quantum phase transition between a two-dimensional superconducting state and an insulating state. Analyses of the magnetotransport properties in the insulating state are consistent with weak localization and do not provide evidence for magnetism. The electric field control of superconductivity demonstrated here opens the way to the development of new mesoscopic superconducting circuits.
Nature 01/2009; 456(7222):624-7. · 36.28 Impact Factor
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ABSTRACT: Superconductivity at the interface between the insulators LaAlO3 and SrTiO3 has been tuned with the electric field effect. The data provide evidence for a two dimensional quantum superconductor to insulator (2D-QSI) transition. Here we explore the compatibility of this phase transition line with Berezinskii-Kosterlitz-Thouless (BKT) behavior and a 2D-QSI transition. In an intermediate regime, limited by a finite size effect, we uncover remarkable consistency with BKT- criticality, weak localization in the insulating state and non-Drude behavior in the normal state. Our estimates for the critical exponents of the 2D-QSI-transition, z =1 and nu=3, suggest that it belongs to the 3D-xy universality class.
08/2008;
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N Reyren,
S Thiel, A D Caviglia,
L Fitting Kourkoutis,
G Hammerl,
C Richter,
C W Schneider,
T Kopp,
A-S Rüetschi,
D Jaccard,
M Gabay,
D A Muller,
J-M Triscone,
J Mannhart
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ABSTRACT: At interfaces between complex oxides, electronic systems with unusual electronic properties can be generated. We report on superconductivity in the electron gas formed at the interface between two insulating dielectric perovskite oxides, LaAlO3 and SrTiO3. The behavior of the electron gas is that of a two-dimensional superconductor, confined to a thin sheet at the interface. The superconducting transition temperature of congruent with 200 millikelvin provides a strict upper limit to the thickness of the superconducting layer of congruent with 10 nanometers.
Science 09/2007; 317(5842):1196-9. · 31.20 Impact Factor
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ABSTRACT: Recently superconductivity at the interface between the insulators LaAlO3 and SrTiO3 has been tuned with the electric-field effect to an unprecedented range of transition temperatures. Here we perform a detailed finite-size scaling analysis to explore the compatibility of the phase-transition line with Berezinskii-Kosterlitz-Thouless (BKT) behavior and a two-dimensional–quantum-phase (2D-QP) transition. In an intermediate regime, limited by a gate voltage dependent limiting length, we uncover remarkable consistency with a BKT-critical line ending at a metallic quantum critical point, separating a weakly localized insulator from the superconducting phase. Our estimates for the critical exponents of the 2D-QP-transition, z≃1 and ν̅ ≃2/3, suggest that it belongs to the three-dimensional-xy universality class.
Phys. Rev. B. 79(18).
