2,179 research outputs found
Reduced leakage current in Josephson tunnel junctions with codeposited barriers
Josephson junctions were fabricated using two different methods of barrier
formation. The trilayers employed were Nb/Al-AlOx/Nb on sapphire, where the
first two layers were epitaxial. The oxide barrier was formed either by
exposing the Al surface to O2 or by codepositing Al in an O2 background. The
codeposition process yielded junctions that showed the theoretically predicted
subgap current and no measurable shunt conductance. In contrast, devices with
barriers formed by thermal oxidation showed a small shunt conductance in
addition to the predicted subgap current.Comment: 3 pages, 4 figure
Electronic reconstruction at SrMnO3-LaMnO3 superlattice interfaces
We use resonant soft x-ray scattering to study electronic reconstruction at
the interface between the Mott insulator LaMnO3 and the "band" insulator
SrMnO3. Superlattices of these two insulators were shown previously to have
both ferromagnetism and metallic tendencies [Koida et al., Phys. Rev. B 66,
144418 (2002)]. By studying a judiciously chosen superlattice reflection we
show that the interface density of states exhibits a pronounced peak at the
Fermi level, similar to that predicted by Okamoto et al. [Phys. Rev. B 70,
241104(R) (2004)]. The intensity of this peak correlates with the conductivity
and magnetization, suggesting it is the driver of metallic behavior. Our study
demonstrates a general strategy for using RSXS to probe the electronic
properties of heterostructure interfaces.Comment: 4.2 pages, 4 figure
Broken particle-hole symmetry at atomically flat a-axis YBa2Cu3O7-d interfaces
We have studied quasiparticle tunneling into atomically flat a-axis films of
YBa2Cu3O7-d and DyBa2Cu3O7-d through epitaxial CaTiO3 barriers. The junction
heterostructures were grown by oxide molecular beam epitaxy and were carefully
optimized using in-situ monitoring techniques, resulting in unprecedented
crystalline perfection of the superconductor/insulator interface. Below Tc, the
tunneling conductance shows the evolution of a large unexpected asymmetrical
feature near zero bias. This is evidence that superconducting YBCO crystals,
atomically truncated along the lobe direction with a titanate layer, have
intrinsically broken particle-hole symmetry over macroscopically large areas.Comment: 15 pages, 4 figures; v2 includes minor changes in concluding
paragraph to match PRL versio
Terahertz-Mediated Microwave-to-Optical Transduction
Transduction of quantum signals between the microwave and the optical ranges
will unlock powerful hybrid quantum systems enabling information processing
with superconducting qubits and low-noise quantum networking through optical
photons. Most microwave-to-optical quantum transducers suffer from thermal
noise due to pump absorption. We analyze the coupled thermal and wave dynamics
in electro-optic transducers that use a two-step scheme based on an
intermediate frequency state in the THz range. Our analysis, supported by
numerical simulations, shows that the two-step scheme operating with a
continuous pump offers near-unity external efficiency with a multi-order noise
suppression compared to direct transduction. As a result, two-step
electro-optic transducers may enable quantum noise-limited interfacing of
superconducting quantum processors with optical channels at MHz-scale bitrates
In-situ strain tuning of the Dirac surface states in Bi2Se3 films
Elastic strain has the potential for a controlled manipulation of the band
gap and spin-polarized Dirac states of topological materials, which can lead to
pseudo-magnetic-field effects, helical flat bands and topological phase
transitions. However, practical realization of these exotic phenomena is
challenging and yet to be achieved. Here, we show that the Dirac surface states
of the topological insulator Bi2Se3 can be reversibly tuned by an externally
applied elastic strain. Performing in-situ x-ray diffraction and in-situ
angle-resolved photoemission spectroscopy measurements during tensile testing
of epitaxial Bi2Se3 films bonded onto a flexible substrate, we demonstrate
elastic strains of up to 2.1% and quantify the resulting reversible changes in
the topological surface state. Our study establishes the functional
relationship between the lattice and electronic structures of Bi2Se3 and, more
generally, demonstrates a new route toward momentum-resolved mapping of
strain-induced band structure changes
Challenges in Ceramic Science: A Report from the Workshop on Emerging Research Areas in Ceramic Science
In March 2012, a group of researchers met to discuss emerging topics in ceramic science and to identify grand challenges in the field. By the end of the workshop, the group reached a consensus on eight challenges for the future:—understanding rare events in ceramic microstructures, understanding the phase-like behavior of interfaces, predicting and controlling heterogeneous microstructures with unprecedented functionalities, controlling the properties of oxide electronics, understanding defects in the vicinity of interfaces, controlling ceramics far from equilibrium, accelerating the development of new ceramic materials, and harnessing order within disorder in glasses. This paper reports the outcomes of the workshop and provides descriptions of these challenges
Gender Gaps in Education and Labor Market Outcomes in the United States: The Impact of Employers' Prejudice
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