422 research outputs found
Dramatic Mobility Enhancements in Doped SrTiO3 Thin Films by Defect Management
We report bulk-quality n-type SrTiO3 (n-SrTiO3) thin films fabricated by
pulsed laser deposition, with electron mobility as high as 6600 cm2 V-1 s-1 at
2 K and carrier density as low as 2.0 x 10^18cm-3 (~ 0.02 at. %), far exceeding
previous pulsed laser deposition films. This result stems from precise
strontium and oxygen vacancy defect chemistry management, providing a general
approach for defect control in complex oxide heteroepitaxy.Comment: 13 pages, 4 figure
Fermi surface and superconductivity in low-density high-mobility {\delta}-doped SrTiO3
The electronic structure of low-density n-type SrTiO3 delta-doped
heterostructures is investigated by angular dependent Shubnikov-de Haas
oscillations. In addition to a controllable crossover from a three- to
two-dimensional Fermi surface, clear beating patterns for decreasing dopant
layer thicknesses are found. These indicate the lifting of the degeneracy of
the conduction band due to subband quantization in the two-dimensional limit.
Analysis of the temperature-dependent oscillations shows that similar effective
masses are found for all components, associated with the splitting of the light
electron pocket. The dimensionality crossover in the superconducting state is
found to be distinct from the normal state, resulting in a rich phase diagram
as a function of dopant layer thickness.Comment: 4 pages, 5 figures, submitted for publicatio
Dominant mobility modulation by the electric field effect at the LaAlO_3 / SrTiO_3 interface
Caviglia et al. [Nature (London) 456, 624 (2008)] have found that the
superconducting LaAlO_3 / SrTiO_3 interface can be gate modulated. A central
issue is to determine the principal effect of the applied electric field. Using
magnetotransport studies of a gated structure, we find that the mobility
variation is almost five times as large as the sheet carrier density.
Furthermore, superconductivity can be suppressed at both positive and negative
gate bias. These results indicate that the relative disorder strength strongly
increases across the superconductor-insulator transition.Comment: 4 pages, 4 figure
Intrinsic spin-orbit coupling in superconducting {\delta}-doped SrTiO3 heterostructures
We report the violation of the Pauli limit due to intrinsic spin-orbit
coupling in SrTiO3 heterostructures. Via selective doping down to a few
nanometers, a two-dimensional superconductor is formed, geometrically
suppressing orbital pair-breaking. The spin-orbit scattering is exposed by the
robust in-plane superconducting upper critical field, exceeding the Pauli limit
by a factor of 4. Transport scattering times several orders of magnitude higher
than for conventional thin film superconductors enables a new regime to be
entered, where spin-orbit coupling effects arise non-perturbatively.Comment: main text 4 pages with 4 figures, supplemental material 2 pages with
2 figure, submitted for publicatio
Single-valley quantum Hall ferromagnet in a dilute Mg_xZn_(1−x)O/ZnO strongly correlated two-dimensional electron system
We investigate the spin susceptibility (g^∗m^∗) of dilute two-dimensional (2D) electrons confined at the Mg_xZn_(1−x)O/ZnO heterointerface. Magnetotransport measurements show a four-fold enhancement of g^∗m^∗, dominated by the increase in the Landé
g-factor. The g-factor enhancement leads to a ferromagnetic instability of the electron gas as evidenced by sharp resistance spikes. At high magnetic field, the large g^∗m^∗ leads to full spin polarization, where we found sudden increase in resistance around the filling factors of half-integer, accompanied by complete disappearance of fractional quantum Hall (QH) states. Along with its large effective mass and the high electron mobility, our result indicates that the ZnO 2D system is ideal for investigating the effect of electron correlations in the QH regime
Single-valley quantum Hall ferromagnet in a dilute Mg_xZn_(1−x)O/ZnO strongly correlated two-dimensional electron system
We investigate the spin susceptibility (g^∗m^∗) of dilute two-dimensional (2D) electrons confined at the Mg_xZn_(1−x)O/ZnO heterointerface. Magnetotransport measurements show a four-fold enhancement of g^∗m^∗, dominated by the increase in the Landé
g-factor. The g-factor enhancement leads to a ferromagnetic instability of the electron gas as evidenced by sharp resistance spikes. At high magnetic field, the large g^∗m^∗ leads to full spin polarization, where we found sudden increase in resistance around the filling factors of half-integer, accompanied by complete disappearance of fractional quantum Hall (QH) states. Along with its large effective mass and the high electron mobility, our result indicates that the ZnO 2D system is ideal for investigating the effect of electron correlations in the QH regime
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