247 research outputs found

    Domain wall roughness in epitaxial ferroelectric PbZr0.2Ti0.8O3 thin films

    Full text link
    The static configuration of ferroelectric domain walls was investigated using atomic force microscopy on epitaxial PbZr0.2Ti0.8O3 thin films. Measurements of domain wall roughness reveal a power law growth of the correlation function of relative displacements B(L) ~ L^(2zeta) with zeta ~ 0.26 at short length scales L, followed by an apparent saturation at large L. In the same films, the dynamic exponent mu was found to be ~ 0.6 from independent measurements of domain wall creep. These results give an effective domain wall dimensionality of d=2.5, in good agreement with theoretical calculations for a two-dimensional elastic interface in the presence of random-bond disorder and long range dipolar interactions.Comment: 5 pages, 4 figure

    Electric field effect modulation of transition temperature, mobile carrier density and in-plane penetration depth in NdBa2Cu3O(7-delta) thin films

    Full text link
    We explore the relationship between the critical temperature, T_c, the mobile areal carrier density, n_2D, and the zero temperature magnetic in-plane penetration depth, lambda_ab(0), in very thin underdoped NdBa2Cu3O{7-delta} films near the superconductor to insulator transition using the electric field effect technique. We observe that T_c depends linearly on both, n_2D and lambda_ab(0), the signature of a quantum superconductor to insulator (QSI) transition in two dimensions with znu-bar where z is the dynamic and nu-bar the critical exponent of the in-plane correlation length.Comment: 4 pages, 4 figure

    Epitaxial growth and transport properties of Nb-doped SrTiO3_{3} thin films

    Full text link
    Nb-doped SrTiO3_{3} epitaxial thin films have been prepared on (001) SrTiO3_{3} substrates using pulsed laser deposition. A high substrate temperature (>1000∘C>1000^{\circ}{C}) was found to be necessary to achieve 2-dimensional growth. Atomic force microscopy reveals atomically flat surfaces with 3.9 \AA steps. The films show a metallic behavior, residual resistivity ratios between 10 and 100, and low residual resistivity of the order of 10−4^{-4}Ω\Omegacm. At 0.3 K, a sharp superconducting transition, reaching zero resistance, is observed.Comment: 4 pages, 4 figure

    Large modulation of the Shubnikov-de Haas oscillations by the Rashba interaction at the LaAlO3_{3}/SrTiO3_{3} interface

    Full text link
    We investigate the 2-dimensional Fermi surface of high-mobility LaAlO3_3/SrTiO3_3 interfaces using Shubnikov-de Haas oscillations. Our analysis of the oscillation pattern underscores the key role played by the Rashba spin-orbit interaction brought about by the breaking of inversion symmetry, as well as the dominant contribution of the heavy dxzd_{xz}/dyzd_{yz} orbitals on electrical transport. We furthermore bring into light the complex evolution of the oscillations with the carrier density, which is tuned by the field effect

    Large phonon-drag enhancement induced by narrow quantum confinement at the LaAlO3/SrTiO3 interface

    Full text link
    The thermoelectric power of the two-dimensional electron system (2DES) at the LaAlO3/SrTiO3 interface is explored below room temperature, in comparison with that of Nb-doped SrTiO3 single crystals. For the interface we find a region below T =50 K where thermopower is dominated by phonon-drag, whose amplitude is hugely amplified with respect to the corresponding bulk value, reaching values ~mV/K and above. The phonon-drag enhancement at the interface is traced back to the tight carrier confinement of the 2DES, and represents a sharp signature of strong electron-acoustic phonon coupling at the interface

    Tunable Rashba spin-orbit interaction at oxide interfaces

    Full text link
    The quasi-two-dimensional electron gas found at the LaAlO3/SrTiO3 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

    Growth-induced electron mobility enhancement at the LaAlO3_3/SrTiO3_3 interface

    Full text link
    We have studied the electronic properties of the 2D electron liquid present at the LaAlO3_3/SrTiO3_3 interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650{\deg}C exhibit the highest low temperature mobility (≈10000 cm2/Vs\approx 10000 \textrm{ cm}^2/\textrm{Vs}) and the lowest sheet carrier density (≈5×1012 cm−2\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{\deg}C) display carrier densities in the range of ≈2−5×1013 cm−2\approx 2-5 \times 10^{13} \textrm{ cm}^{-2} and mobilities of ≈1000 cm2/Vs\approx 1000 \textrm{ cm}^2/\textrm{Vs} at 4K. Reducing their carrier density by field effect to 8×1012 cm−28\times 10^{12} \textrm{ cm}^{-2} lowers their mobilites to ≈50 cm2/Vs\approx 50 \textrm{ cm}^2/\textrm{Vs} bringing the conductance to the weak-localization regime

    Optical spectroscopy and the nature of the insulating state of rare-earth nickelates

    Full text link
    Using a combination of spectroscopic ellipsometry and DC transport measurements, we determine the temperature dependence of the optical conductivity of NdNiO3_3 and SmNiO3_{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.Comment: 12 pages, 13 figure
    • …
    corecore