247 research outputs found
Domain wall roughness in epitaxial ferroelectric PbZr0.2Ti0.8O3 thin films
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
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 SrTiO thin films
Nb-doped SrTiO epitaxial thin films have been prepared on (001)
SrTiO substrates using pulsed laser deposition. A high substrate
temperature () 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 10cm. 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 LaAlO/SrTiO interface
We investigate the 2-dimensional Fermi surface of high-mobility
LaAlO/SrTiO 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 /
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
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
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 LaAlO/SrTiO interface
We have studied the electronic properties of the 2D electron liquid present
at the LaAlO/SrTiO 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 () and the lowest sheet carrier density (). 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
and mobilities of at 4K. Reducing their carrier density by field
effect to lowers their mobilites to
bringing the conductance to the
weak-localization regime
Optical spectroscopy and the nature of the insulating state of rare-earth nickelates
Using a combination of spectroscopic ellipsometry and DC transport
measurements, we determine the temperature dependence of the optical
conductivity of NdNiO and SmNiO 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
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