1,424 research outputs found
Checkerboard order in the t--J model on the square lattice
We propose that the inhomogeneous patterns seen by STM in some underdoped
superconducting cuprates could be related to a bond-order-wave instability of
the staggered flux state, one of the most studied "normal" state proposed to
compete with the d-wave RVB superconductor. A checkerboard pattern is obtained
by a Gutzwiller renormalized mean-field theory of the t-J model for doping
around 1/8. It is found that the charge modulation is always an order of
magnitude smaller than the bond-order modulations. This is confirmed by an
exact optimization of the wavefunction by a variational Monte Carlo scheme. The
numerical estimates of the order parameters are however found to be strongly
reduced w.r.t their mean-field values
Quantum transport signatures of chiral edge states in SrRuO
We investigate transport properties of a double quantum dot based Cooper pair
splitter, where the superconducting lead consists of SrRuO. The
proposed device can be used to explore the symmetry of the superconducting
order parameter in SrRuO by testing the presence of gapless chiral edge
states, which are predicted to exist if the bulk superconductor is described by
a chiral --wave state. The odd orbital symmetry of the bulk order parameter
ensures that we can realize a regime where the electrons tunneling into the
double dot system come from the chiral edge states and thereby leave their
signature in the conductance. The proposed Cooper pair splitter has the
potential to probe order parameters in unconventional superconductors.Comment: 5 page
Bond order wave instabilities in doped frustrated antiferromagnets: "Valence bond solids" at fractional filling
We explore both analytically and numerically the properties of doped t-J
models on a class of highly frustrated lattices, such as the kagome and the
pyrochlore lattice. Focussing on a particular sign of the hopping integral and
antiferromagnetic exchange, we find a generic symmetry breaking instability
towards a twofold degenerate ground state at a fractional filling below half
filling. These states show modulated bond strengths and only break lattice
symmetries. They can be seen as a generalization of the well-known valence bond
solid states to fractional filling.Comment: slightly shortened and reorganized versio
Multiple layer local oxidation for fabricating semiconductor nanostructures
Coupled semiconductor nanostructures with a high degree of tunability are
fabricated using local oxidation with a scanning force microscope. Direct
oxidation of the GaAs surface of a Ga[Al]As heterostructure containing a
shallow two-dimensional electron gas is combined with the local oxidation of a
thin titanium film evaporated on top. A four-terminal quantum dot and a double
quantum dot system with integrated charge readout are realized. The structures
are tunable via in-plane gates formed by isolated regions in the electron gas
and by mutually isolated regions of the Ti film acting as top gates. Coulomb
blockade experiments demonstrate the high quality of this fabrication process.Comment: 3 pages, 3 figure
Screw- and nail-gluing techniques for wood composite structures
Composite systems enhance the structural capacity and reliability of wood solutions for structures. With today engineered wood products and structural adhesives, high performing structures can be constructed. Hybrid assembly techniques that combine mechanical fasteners and an adhesive (screw- and nailgluing techniques) allow manufacturing large dimension composite structures with reasonable infrastructure. They also give full composite properties to the interlayers. Furthermore, these hybrid connections can experience ductility. This paper presents a research on small-scale glued assemblies which were manufactured using screw- and nail-gluing techniques. It discusses qualitative and quantitative analyses that confirmed the full-composite properties and ductility of the interlayers. The analyses also show that superposing the behaviour of both connectors is reasonable to predict the strength and slip modulus of hybrid connections. © 2007 Taylor & Francis Group, London
Understanding the composite characteristics of stressed-skin panels
The composite properties of stressed-skin panel (SSP) systems are characterised by the interaction ? composite action ? and the portion of the sheathing acting with the joists ? the tributary width. A discussion on the tributary width forms the focus of this paper. An analysis, which has been conducted considering the pattern of the strain distribution in the sheathing(s), is presented. It uses laboratory data of a major research project conducted at the University of Technology, Sydney, between 2002 and 2007 (Gerber 2007). This analysis indicates that under strict conditions, in particular structurally glued interlayers, a large portion of the sheathing contributes to the structural behaviour of SSP structures. A better use of the mechanical properties of the panels is also achieved. This paper also presents an analysis on the effects of discontinuities in the sheathing. It has been identified that such event causes a significant reduction of the sheathing contribution
Quasiparticle Dynamics in the Kondo Lattice Model at Half Filling
We study spectral properties of quasiparticles in the Kondo lattice model in
one and two dimensions including the coherent quasiparticle dispersions, their
spectral weights and the full two-quasiparticle spectrum using a cluster
expansion scheme. We investigate the evolution of the quasiparticle band as
antiferromagnetic correlations are enhanced towards the RKKY limit of the
model. In both the 1D and the 2D model we find that a repulsive interaction
between quasiparticles results in a distinct antibound state above the
two-quasiparticle continuum. The repulsive interaction is correlated with the
emerging antiferromagnetic correlations and can therefore be associated with
spin fluctuations. On the square lattice, the antibound state has an extended
s-wave symmetry.Comment: 8 pages, 11 figure
Computer Simulations of Timber-stressed Skin Panels Using Finite Elements
A Finite Element Model (FEM) can provide a helpful and accurate tool for acquiring a better understanding of complex structures such stressed skin panel (SSP) systems and can contribute towards saving costly experiments. Because SSP constructions are highly complex, orthotropic, statically indeterminate and multi-layer assemblies and their members are orthotropic, and have viscoelastic properties and non-linear behaviour under certain conditions, accommodating SSP systems into a FEM is an arduous task and inevitably represents an idealisation of the physical structures
In Situ Treatment of a Scanning Gate Microscopy Tip
In scanning gate microscopy, where the tip of a scanning force microscope is
used as a movable gate to study electronic transport in nanostructures, the
shape and magnitude of the tip-induced potential are important for the
resolution and interpretation of the measurements. Contaminations picked up
during topography scans may significantly alter this potential. We present an
in situ high-field treatment of the tip that improves the tip-induced
potential. A quantum dot was used to measure the tip-induced potential.Comment: 3 pages, 1 figure, minor changes to fit published versio
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