268 research outputs found
Observability of surface Andreev bound states in a topological insulator in proximity to an s-wave superconductor
To guide experimental work on the search for Majorana zero-energy modes, we
calculate the superconducting pairing symmetry of a three-dimensional
topological insulator in combination with an s-wave superconductor. In analogy
to the case of nanowires with strong spin-orbit coupling we show how the
pairing symmetry changes across different topological regimes. We demonstrate
that a dominant p-wave pairing relation is not sufficient to realize a Majorana
zero-energy mode useful for quantum computation. Our main result of this paper
is the relation between odd-frequency pairing and Majorana zero energy modes by
using Green functions techniques in three-dimensional topological insulators in
the so-called Majorana regime. We discuss thereafter how the pairing relations
in the different regimes can be observed in the shape of the tunneling
conductance of an s-wave proximized three-dimensional topological insulator. We
will discuss the necessity to incorporate a ferromagnetic insulator to localize
the zero-energy bound state to the interface as a Majorana mode.Comment: Accepted for publication in Journal of Physics: Condensed Matte
Nonlocal Andreev reflection, fractional charge and current-phase relation in topological bilayer exciton condensate junctions
We study Andreev reflection and Josephson currents in topological bilayer
exciton condensates (TEC). These systems can create 100% spin entangled
nonlocal currents with high amplitudes due to perfect nonlocal Andreev
reflection. This Andreev reflection process can be gate tuned from a regime of
purely retro reflection to purely specular reflection. We have studied the
bound states in TEC-TI-TEC Josephson junctions and find a gapless dispersion
for perpendicular incidence. The presence of a sharp transition in the
supercurrent-phase relationship when the system is in equilibrium is a
signature of fractional charge, which can be further revealed in ac
measurements faster than relaxation processes via Landau-Zener processes.Comment: Submitted to Physical Review
Short-term Mortality and Postoperative Complications of Abdominal Aortic Aneurysm Repair in Obese versus Non-obese Patients
BACKGROUND: Obesity is a risk factor not only for abdominal aortic aneurysm (AAA) but also for complications after vascular surgery. This study was to determine the effect of obesity on short-term mortality and post-intervention complications after AAA repair. METHODS: A systematic review and meta-analysis were performed. A systematic search was performed in PubMed; the articles describing the differences in post-intervention complications after open or endovascular repair of an AAA between obese and non-obese patients were selected. The primary outcome was short-term mortality defined as in-hospital mortality or mortality within 30 days after AAA repair. The secondary outcomes were cardiac complications, pulmonary failure, renal failure, and wound infections. The meta-analysis was performed using OpenMeta. RESULTS: Four articles were included in the meta-analysis; these articles included 35,989 patients of which 10,917 (30.3%) were obese. The meta-analysis showed no significant differences for short-term mortality (odds ratio [OR], 0.85; 95% confidence interval [CI], 0.69–1.04). Also, no significant difference was found in pulmonary failure (OR, 1.09; 95% CI, 0.85–1.42). However, obese patients were less likely to suffer from cardiac complications (OR, 0.73; 95% CI, 0.55–0.96). Nevertheless, there was a significantly higher risk of renal failure (OR, 1.16; 95% CI, 1.05–1.30) and wound infections (OR, 1.92; 95% CI, 1.55–2.38) in obese patients. CONCLUSION: Obesity is not a risk factor for short-term mortality after AAA repair compared to non-obesity. Moreover, obese patients suffer less from cardiac complications than non-obese patients
Josephson supercurrent in a topological insulator without a bulk shunt
A Josephson supercurrent has been induced into the three-dimensional
topological insulator Bi1.5Sb0.5Te1.7Se1.3. We show that the transport in
Bi1.5Sb0.5Te1.7Se1.3 exfoliated flakes is dominated by surface states and that
the bulk conductivity can be neglected at the temperatures where we study the
proximity induced superconductivity. We prepared Josephson junctions with
widths in the order of 40 nm and lengths in the order of 50 to 80 nm on several
Bi1.5Sb0.5Te1.7Se1.3 flakes and measured down to 30 mK. The Fraunhofer patterns
unequivocally reveal that the supercurrent is a Josephson supercurrent. The
measured critical currents are reproducibly observed on different devices and
upon multiple cooldowns, and the critical current dependence on temperature as
well as magnetic field can be well explained by diffusive transport models and
geometric effects
Optimal Redesign of the Dutch Road Network
The Dutch national road network has been developed over several decades. In the past, roads were constructed according to the then current spatial and transportation planning philosophies. Because the existing road network is a result of a long process of successive developments, the question can be asked whether this network is the most appropriate from the current point of view, especially taking in consideration the current socio economic structure of the Netherlands. To answer this question an optimization algorithm for designing road networks has been developed. With this algorithm the Dutch road network has been redesigned based on minimization of the travel and infrastructure costs and by taking into account the socio economic structure of the Netherlands. A comparison between the existing network and the new design shows that the redesigned Dutch national road network has significantly lower total costs than the existing road network. It is found that the construction of less roads with more lanes on different locations leads to a reduction of the total travel time and the total vehicles kilometers traveled
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