94 research outputs found
Ultra‐high elastic strain energy storage in hybrid metal‐oxide infiltrated polymer nanocomposites
An understanding of the mechanical properties of materials at nanometer length scales, including a material’s ability to store and release elastic strain energy, is of great significance in the effective miniaturization of actuators, sensors and resonators for use in micro-/nano-electromechanical systems (MEMS/NEMS) as well as advanced development of artificial muscles for locomotion in soft robots. The measure of a material’s ability to store and release elastic strain energy, the modulus of resilience (R), is a crucial parameter in realizing such advanced mechanical actuation technologies. Typically, engineering a material system with a large R requires large increases in the material’s yield strength yet conservative increase in Young’s modulus, an engineering challenge as the two mechanical properties are strongly coupled; generally, strengthening methods results in considerable stiffening or increase in the Young’s modulus. Here, we present hybrid composite polymer nanopillars which achieve the highest specific R ever reported, by utilizing vapor-phase aluminum oxide infiltrations into lithographically patterned polymer resist SU-8. In-situ nanomechanical measurements reveal high, metallic-like yield strengths (~500 MPa) combined with a compliant, polymeric-like Young’s modulus (~7 GPa), a unique pairing never observed in known engineering materials. It is these exceptional elastic properties of our hybrid composite which allows for realization of R per density (Rs) values ~ 11200 J/kg, orders of magnitude greater than those in most engineering material systems. The high elastic energy storage/release capability of this material, as well as its compatibility with lithographic techniques, makes it an attractive candidate in the design of MEMS devices, which require an ultra-high elastic component for advanced actuation and sensor technologies. Furthermore, an opportunity for tunability of the elastic properties of the SU-8 polymeric material exists with this fabrication technique by varying the number of infiltration cycles or the organometallic precursor
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The study of contact properties in edge-contacted graphene-aluminum Josephson junctions
Transparent contact interfaces in superconductor-graphene hybrid systems are
critical for realizing superconducting quantum applications. Here, we examine
the effect of the edge-contact fabrication process on the transparency of the
superconducting aluminum-graphene junction. We show significant improvement in
the transparency of our superconductor-graphene junctions by promoting the
chemical component of the edge contact etch process. Our results compare
favorably with state-of-the-art graphene Josephson junctions. The findings of
our study contribute to advancing the fabrication knowledge of edge-contacted
superconductor-graphene junctions
Anisotropy of Antiferromagnetic Domains in a Spin-orbit Mott Insulator
The temperature-dependent behavior of magnetic domains plays an essential
role in the magnetic properties of materials, leading to widespread
applications. However, experimental methods to access the three-dimensional
(3D) magnetic domain structures are very limited, especially for
antiferromagnets. Over the past decades, the spin-orbit Mott insulator iridate
has attracted particular attention because of its interesting
magnetic structure and analogy to superconducting cuprates. Here, we apply
resonant x-ray magnetic Bragg coherent diffraction imaging to track the
real-space 3D evolution of antiferromagnetic ordering inside a
single crystal as a function of temperature, finding that the antiferromagnetic
domain shows anisotropic changes. The anisotropy of the domain shape reveals
the underlying anisotropy of the antiferromagnetic coupling strength within
. These results demonstrate the high potential significance of 3D
domain imaging in magnetism research
Evaporation and Condensation of Clusters
Influence of surrounding matter on the properties of clusters is considered
by an approach combining the methods of statistical and quantum mechanics. A
cluster is treated as a bound N-particle system and surrounding matter as
thermostat. It is shown that, despite arbitrary strong interactions between
particles, cluster energy can be calculated by using the controlled
perturbation theory. The accuracy of the latter is found to be much higher than
that of the quasiclassical approximation. Spectral distribution is obtained by
minimizing conditional entropy. Increasing the thermostat temperature leads to
the depletion of bound states. The characteristic temperature when bound states
become essentially depleated defines the temperature of cluster evaporation.
The inverse process of lowering the thermostate temperature, yielding the
filling of bound states, corresponds to cluster condensation.Comment: 1 file, 15 pages, RevTex, 4 table
Microscopic Relaxation Channels in Materials for Superconducting Qubits
Despite mounting evidence that materials imperfections are a major obstacle
to practical applications of superconducting qubits, connections between
microscopic material properties and qubit coherence are poorly understood.
Here, we perform measurements of transmon qubit relaxation times in
parallel with spectroscopy and microscopy of the thin polycrystalline niobium
films used in qubit fabrication. By comparing results for films deposited using
three techniques, we reveal correlations between and grain size, enhanced
oxygen diffusion along grain boundaries, and the concentration of suboxides
near the surface. Physical mechanisms connect these microscopic properties to
residual surface resistance and through losses arising from the grain
boundaries and from defects in the suboxides. Further, experiments show that
the residual resistance ratio can be used as a figure of merit for qubit
lifetime. This comprehensive approach to understanding qubit decoherence charts
a pathway for materials-driven improvements of superconducting qubit
performance
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