Showing papers by "Jean-Marc Triscone published in 2015"
TL;DR: In this paper, a femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering in complex oxide heterostructures.
Abstract: Static strain in complex oxide heterostructures1, 2 has been extensively used to engineer electronic and magnetic properties at equilibrium3. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across heterointerfaces dynamically4. Here, by exciting large-amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a heterointerface. Femtosecond resonant soft X-ray diffraction is used to determine the spatiotemporal evolution of the magnetic disordering. We observe a magnetic melt front that propagates from the substrate interface into the film, at a speed that suggests electronically driven motion. Light control and ultrafast phase front propagation at heterointerfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices.
116 citations
TL;DR: Using a variety of synchrotron-based techniques, it is shown that the degree of intermixing at the monolayer scale allows interface-driven properties such as charge transfer and the induced magnetic moment in the nickelate layer to be controlled.
Abstract: The functional properties of oxide heterostructures ultimately rely on how the electronic and structural mismatches occurring at interfaces are accommodated by the chosen materials combination. We discuss here LaMnO3/LaNiO3 heterostructures, which display an intrinsic interface structural asymmetry depending on the growth sequence. Using a variety of synchrotron-based techniques, we show that the degree of intermixing at the monolayer scale allows interface-driven properties such as charge transfer and the induced magnetic moment in the nickelate layer to be controlled. Further, our results demonstrate that the magnetic state of strained LaMnO3 thin films dramatically depends on interface reconstructions.
94 citations
TL;DR: In this article, the authors demonstrate that by modifying the screening at the metal-ferroelectric interface through insertion of ultrathin dielectric spacers, the strength of the depolarization field can be tuned and thus used to control the formation of nanoscale domains.
Abstract: The screening efficiency of a metal-ferroelectric interface plays a critical role in determining the polarization stability and hence the functional properties of ferroelectric thin films. Imperfect screening leads to strong depolarization fields that reduce the spontaneous polarization or drive the formation of ferroelectric domains. We demonstrate that by modifying the screening at the metal-ferroelectric interface through insertion of ultrathin dielectric spacers, the strength of the depolarization field can be tuned and thus used to control the formation of nanoscale domains. Using piezoresponse force microscopy, we follow the evolution of the domain configurations as well as polarization stability as a function of depolarization field strength.
91 citations
TL;DR: In this article, a femtosecond Resonant Soft X-ray Diffraction (FRSD) was used to determine the spatial and temporal evolution of the magnetic disordering.
Abstract: Static strain in complex oxide heterostructures has been extensively used to engineer electronic and magnetic properties at equilibrium. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across hetero-interfaces dynamically. Here, by exciting large amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a hetero-interface. Femtosecond Resonant Soft X-ray Diffraction is used to determine the spatial and temporal evolution of the magnetic disordering. We observe a magnetic melt front that grows from the substrate interface into the film, at a speed that suggests electronically driven propagation. Light control and ultrafast phase front propagation at hetero-interfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices.
82 citations
TL;DR: This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface, which is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures.
Abstract: Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 104–105μVK−1, oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface.
67 citations
TL;DR: In this article, the authors investigate thin films of SmNiO_3 subjected to different levels of epitaxial strain and find that the original bulk behavior (T_N\'eel
Abstract: Nickelates are known for their metal to insulator transition (MIT) and an unusual magnetic ordering, occurring at T=T_N\'eel. Here, we investigate thin films of SmNiO_3 subjected to different levels of epitaxial strain. We find that the original bulk behavior (T_N\'eel
65 citations
TL;DR: The experimental findings on the origin and the extension of the electron liquid are reviewed, the theoretical models developed to describe the charge profile and the band structure are discussed and a model to account for the effect of interface disorder which could modify the charge distribution is introduced.
Abstract: Physical and structural phenomena originating from polar discontinuities have generated enormous activity. In the last ten years, the oxide interface between polar and non-polar , 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.
57 citations
TL;DR: In this paper, the electronic properties of the 2D electron liquid present at the LaAlO3/SrTiO3 interface in series of samples prepared at different growth temperatures were studied.
Abstract: 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.
51 citations
TL;DR: In this article, the authors show that NdNiO3 and thin films grown along the pseudocubic (001)pc axis display a 1st order metal to insulator transition (MIT) together with a Neel transition at T = 200 K.
Abstract: Bulk NdNiO3 and thin films grown along the pseudocubic (001)pc axis display a 1st order metal to insulator transition (MIT) together with a Neel transition at T = 200 K. Here, we show that for NdNiO3 films deposited on (111)pc NdGaO3, the MIT occurs at T = 335 K and the Neel transition at T = 230 K. By comparing transport and magnetic properties of layers grown on substrates with different symmetries and lattice parameters, we demonstrate a particularly large tuning when the epitaxy is realized on (111)pc surfaces. We attribute this effect to the specific lattice matching conditions imposed along this direction when using orthorhombic substrates.
51 citations
TL;DR: In this paper, the authors employed x-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) at the Ni and Mn L3,2 edges in LaMnO3/LaNiO3 superlattices grown along (001) and (111) orientations.
Abstract: We have employed x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) at the Ni and Mn L3,2 edges in LaMnO3/LaNiO3 superlattices grown along (001) and (111) orientations. Our results show a significant XMCD signal and thus the presence of magnetic moments localized on both Ni and Mn, which are ferromagnetically coupled to each other. X-ray absorption experiments reveal a charge transfer between Ni and Mn which is larger for (111) than for (001) superlattices. These results are compared to theoretical predictions for such superlattices.
49 citations
TL;DR: In this paper, it was shown that the metal-to-insulator transition occurs at T =335K and the Neel transition at T=230 K on the pseudocubic (001)pc axis.
Abstract: Bulk NdNiO_3 and thin films grown along the pseudocubic (001)_pc axis display a 1st order metal to insulator transition (MIT) together with a Neel transition at T=200K. Here, we show that for NdNiO3 films deposited on (111)_pc NdGaO_3 the MIT occurs at T=335K and the Neel transition at T=230 K. By comparing transport and magnetic properties of layers grown on substrates with different symmetries and lattice parameters, we demonstrate a particularly large tuning when the epitaxy is realized on (111)_pc surfaces. We attribute this effect to the specific lattice matching conditions imposed along this direction when using orthorhombic substrates.
TL;DR: In this article, a detailed analysis of magneto-transport properties of top and back-gated LaAlO3/SrTiO3 heterostructures is presented.
Abstract: 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.
TL;DR: In this article, a combination of spectroscopic ellipsometry and DC transport measurements was used to determine the temperature dependence of the optical conductivity of NdNiO and SmNiO films.
Abstract: Using a combination of spectroscopic ellipsometry and DC transport measurements, we determine the temperature dependence of the optical conductivity of ${\mathrm{NdNiO}}_{3}$ and ${\mathrm{SmNiO}}_{3}$ films. The optical spectra show the appearance of a characteristic two-peak structure in the near-infrared when the material passes from the metal to the insulator phase. Dynamical mean-field theory calculations confirm this two-peak structure and allow us to identify these spectral changes and the associated changes in the electronic structure. We demonstrate that the insulating phase in these compounds and the associated characteristic two-peak structure are due to the combined effect of bond disproportionation and Mott physics associated with half of the disproportionated sites. We also provide insights into the structure of excited states above the gap.
TL;DR: In this article, the electronic properties of the 2D electron liquid present at the LaAlO$_3$/SrTiO$-3$ interface were studied in series of samples prepared at different growth temperatures.
Abstract: We have studied the electronic properties of the 2D electron liquid present at the LaAlO$_3$/SrTiO$_3$ interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650°C exhibit the highest low temperature mobility ($\approx 10000 \textrm{ cm}^2/\textrm{Vs}$) and the lowest sheet carrier density ($\approx 5\times 10^{12} \textrm{ cm}^{-2}$). 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 $\approx 2-5 \times 10^{13} \textrm{ cm}^{-2}$ and mobilities of $\approx 1000 \textrm{ cm}^2/\textrm{Vs}$ at 4K. Reducing their carrier density by field effect to $8\times 10^{12} \textrm{ cm}^{-2}$ lowers their mobilites to $\approx 50 \textrm{ cm}^2/\textrm{Vs}$ bringing the conductance to the weak-localization regime.
TL;DR: In this article, the first successful realization of a superconducting 2DEG at interfaces between artificially-grown LaAlO$_3$ and SrTiO$-3$ thin films was reported.
Abstract: Realization of a fully metallic two-dimensional electron gas at the interface between artificially-grown LaAlO$_3$ and SrTiO$_3$ thin films has been an exciting challenge. Here we present for the first time the successful realization of a superconducting 2DEG at interfaces between artificially-grown LaAlO$_3$ and SrTiO$_3$ thin films. Our results highlight the importance of two factors-the growth temperature and the SrTiO$_3$ termination. We use local friction force microscopy and transport measurements to determine that in normal growth conditions the absence of a robust metallic state at low temperature in the artificially-grown LaAlO$_3$/SrTiO$_3$ interface is due to the nanoscale SrO segregation occurring on the SrTiO$_3$ film surface during the growth and the associated defects in the SrTiO$_3$ film. By adopting an extremely high SrTiO$_3$ growth temperature, we demonstrate a way to realize metallic, down to the lowest temperature, and superconducting 2DEG at interfaces between LaAlO$_3$ layers and artificially-grown SrTiO$_3$ thin films. This study paves the way to the realization of functional LaAlO$_3$/SrTiO$_3$ superlattices and/or artificial LaAlO$_3$/SrTiO$_3$ interfaces on other substrates.
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TL;DR: In this article, a combination of spectroscopic ellipsometry and DC transport measurements was used to determine the temperature dependence of the optical conductivity of NdNiO$_3$ and SmNiO $3}$ films, showing the appearance of a characteristic two-peak structure in the near-infrared when the material passes from the metal to the insulator phase.
Abstract: Using a combination of spectroscopic ellipsometry and DC transport measurements, we determine the temperature dependence of the optical conductivity of NdNiO$_3$ and SmNiO$_{3}$ films. The optical spectra show the appearance of a characteristic two-peak structure in the near-infrared when the material passes from the metal to the insulator phase. Dynamical mean-field theory calculations confirm this two-peak structure, and allow to identify these spectral changes and the associated changes in the electronic structure. We demonstrate that the insulating phase in these compounds and the associated characteristic two-peak structure are due to the combined effect of bond-disproportionation and Mott physics associated with half of the disproportionated sites. We also provide insights into the structure of excited states above the gap.
TL;DR: In this article, a detailed analysis of magneto-transport properties of top and back-gated LaAlO$_3$/SrTiO$-3$ heterostructures is presented.
Abstract: We report a detailed analysis of magneto-transport properties of top- and back-gated LaAlO$_3$/SrTiO$_3$ 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.