8,435 research outputs found
Uniaxial Strain Induced Topological Phase Transition in Bismuth-Tellurohalide-Graphene Heterostructures
We explore the electronic structure and topological phase diagram of
heterostructures formed of graphene and ternary bismuth tellurohalide layers.
We show that mechanical strain inherently present in fabricated samples could
induce a topological phase transition in single-sided heterostructures, turning
the sample into a novel experimental realisation of a time reversal invariant
topological insulator. We construct an effective tight binding description for
low energy excitations and fit the model's parameters to ab initio band
structures. We propose a simple approach for predicting phase boundaries as a
function of mechanical distortions and hence gain a deeper understanding on how
the topological phase in the considered system may be engineered.Comment: 20 pages, 7 figures, Accepted Manuscrip
High-resolution 3D optical microscopy inside the beating zebrafish heart using prospective optical gating
3D fluorescence imaging is a fundamental tool in the study of functional and developmental biology, but effective imaging is particularly difficult in moving structures such as the beating heart. We have developed a non-invasive real-time optical gating system that is able to exploit the periodic nature of the motion to acquire high resolution 3D images of the normally-beating zebrafish heart without any unnecessary exposure of the sample to harmful excitation light. In order for the image stack to be artefact-free, it is essential to use a synchronization source that is invariant as the sample is scanned in 3D. We therefore describe a scheme whereby fluorescence image slices are scanned through the sample while a brightfield camera sharing the same objective lens is maintained at a fixed focus, with correction of sample drift also included. This enables us to maintain, throughout an extended 3D volume, the same standard of synchronization we have previously demonstrated in and near a single 2D plane. Thus we are able image the complete beating zebrafish heart exactly as if the heart had been artificially stopped, but sidestepping this undesirable interference with the heart and instead allowing the heart to beat as normal
Monolayer MoS2 strained to 1.3% with a microelectromechanical system
We report on a modified transfer technique for atomically thin materials integrated onto microelectromechanical
systems (MEMS) for studying strain physics and creating strain-based devices. Our method tolerates the non-planar
structures and fragility of MEMS, while still providing precise positioning and crack free transfer of flakes. Further,
our method used the transfer polymer to anchor the 2D crystal to the MEMS, which reduces the fabrication time,
increases the yield, and allowed us to exploit the strong mechanical coupling between 2D crystal and polymer to
strain the atomically thin system. We successfully strained single atomic layers of molybdenum disulfide (MoS2) with
MEMS devices for the first time and achieved greater than 1.3% strain, marking a major milestone for incorporating
2D materials with MEMS We used the established strain response of MoS2 Raman and Photoluminescence spectra to
deduce the strain in our crystals and provide a consistency check. We found good comparison between our experiment
and literature.Published versio
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