24,249 research outputs found
Efficient Schemes for Reducing Imperfect Collective Decoherences
We propose schemes that are efficient when each pair of qubits undergoes some
imperfect collective decoherence with different baths. In the proposed scheme,
each pair of qubits is first encoded in a decoherence-free subspace composed of
two qubits. Leakage out of the encoding space generated by the imperfection is
reduced by the quantum Zeno effect. Phase errors in the encoded bits generated
by the imperfection are reduced by concatenation of the decoherence-free
subspace with either a three-qubit quantum error correcting code that corrects
only phase errors or a two-qubit quantum error detecting code that detects only
phase errors, connected with the quantum Zeno effect again.Comment: no correction, 3 pages, RevTe
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
Stoichiometry control of the electronic properties of the LaAlO_3/SrTiO_3 heterointerface
We investigate the effect of the laser parameters of pulsed laser deposition
on the film stoichiometry and electronic properties of LaAlO_3/SrTiO_3 (001)
heterostructures. The La/Al ratio in the LaAlO_3 films was varied over a wide
range from 0.88 to 1.15, and was found to have a strong effect on the interface
conductivity. In particular, the carrier density is modulated over more than
two orders of magnitude. The film lattice expansion, caused by cation
vacancies, is found to be the important functional parameter. These results can
be understood to arise from the variations in the electrostatic boundary
conditions, and their resolution, with stoichiometry.Comment: 4 pages, 3 figures, submitted for publicatio
Modulation Doping of a Mott Quantum Well by a Proximate Polar Discontinuity
We present evidence for hole injection into LaAlO3/LaVO3/LaAlO3 quantum wells
near a polar surface of LaAlO3 (001). As the surface is brought in proximity to
the LaVO3 layer, an exponential drop in resistance and a decreasing positive
Seebeck coefficient is observed below a characteristic coupling length of 10-15
unit cells. We attribute this behavior to a crossover from an atomic
reconstruction of the AlO2-terminated LaAlO3 surface to an electronic
reconstruction of the vanadium valence. These results suggest a general
approach to tunable hole-doping in oxide thin film heterostructures.Comment: 16 pages, 7 figure
Negative Differential Resistance Induced by Mn Substitution at SrRuO3/Nb:SrTiO3 Schottky Interfaces
We observed a strong modulation in the current-voltage characteristics of
SrRuO/Nb:SrTiO Schottky junctions by Mn substitution in SrRuO,
which induces a metal-insulator transition in bulk. The temperature dependence
of the junction ideality factor indicates an increased spatial inhomogeneity of
the interface potential with substitution. Furthermore, negative differential
resistance was observed at low temperatures, indicating the formation of a
resonant state by Mn substitution. By spatially varying the position of the Mn
dopants across the interface with single unit cell control, we can isolate the
origin of this resonant state to the interface SrRuO layer. These results
demonstrate a conceptually different approach to controlling interface states
by utilizing the highly sensitive response of conducting perovskites to
impurities
Temperature Dependent Polarity Reversal in Au/Nb:SrTiO3 Schottky Junctions
We have observed temperature-dependent reversal of the rectifying polarity in
Au/Nb:SrTiO3 Schottky junctions. By simulating current-voltage characteristics
we have found that the permittivity of SrTiO3 near the interface exhibits
temperature dependence opposite to that observed in the bulk, significantly
reducing the barrier width. At low temperature, tunneling current dominates the
junction transport due both to such barrier narrowing and to suppressed thermal
excitations. The present results demonstrate that novel junction properties can
be induced by the interface permittivity
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
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