11,313 research outputs found
Mapping the dynamic interactions between vortex species in highly anisotropic superconductors
Here we use highly sensitive magnetisation measurements performed using a
Hall probe sensor on single crystals of highly anisotropic high temperature
superconductors to study the dynamic interactions
between the two species of vortices that exist in such superconductors. We
observe a remarkable and clearly delineated high temperature regime that
mirrors the underlying vortex phase diagram. Our results map out the parameter
space over which these dynamic interaction processes can be used to create
vortex ratchets, pumps and other fluxonic devices.Comment: 7 pages, 3 figures, to be published in Supercond. Sci. Techno
Spintronics in 2D graphene-based van der Waals heterostructures
Spintronics has become a broad and important research field that intersects
with magnetism, nano-electronics, and materials science. Its overarching aim is
to provide a fundamental understanding of spin-dependent phenomena in
solid-state systems that can enable a new generation of spin-based logic
devices. Over the past decade, graphene and related 2D van der Waals crystals
have taken center stage in expanding the scope and potential of spintronic
materials. Their distinctive electronic properties and atomically thin nature
have opened new opportunities to probe and manipulate internal electronic
degrees of freedom. Purely electrical control over conduction-electron spins
can be attained in graphene-transition metal dichalcogenide heterostructures,
due to proximity effects combined with graphene's high electronic mobility.
Specifically, graphene experiences a proximity-induced spin-orbit coupling that
enables efficient spin-charge interconversion processes; the two most
well-known and at the forefront of current research are the spin Hall and
inverse spin galvanic effects, wherein an electrical current yields a spin
current and non-equilibrium spin polarization, respectively. This article
provides an overview of the basic principles, theory, and experimental methods
underpinning the nascent field of 2D material-based spintronics.Comment: 35 pages, 9 figures. To appear in the Encyclopedia of Condensed
Matter Physics Second Editio
Single polymer dynamics: coil-stretch transition in a random flow
By quantitative studies of statistics of polymer stretching in a random flow
and of a flow field we demonstrate that the stretching of polymer molecules in
a 3D random flow occurs rather sharply via the coil-stretch transition at the
value of the criterion close to theoretically predicted.Comment: 4 pages, 5 figure
Velocity and processivity of helicase unwinding of double-stranded nucleic acids
Helicases are molecular motors which unwind double-stranded nucleic acids
(dsNA) in cells. Many helicases move with directional bias on single-stranded
(ss) nucleic acids, and couple their directional translocation to strand
separation. A model of the coupling between translocation and unwinding uses an
interaction potential to represent passive and active helicase mechanisms. A
passive helicase must wait for thermal fluctuations to open dsNA base pairs
before it can advance and inhibit NA closing. An active helicase directly
destabilizes dsNA base pairs, accelerating the opening rate. Here we extend
this model to include helicase unbinding from the nucleic-acid strand. The
helicase processivity depends on the form of the interaction potential. A
passive helicase has a mean attachment time which does not change between ss
translocation and ds unwinding, while an active helicase in general shows a
decrease in attachment time during unwinding relative to ss translocation. In
addition, we describe how helicase unwinding velocity and processivity vary if
the base-pair binding free energy is changed.Comment: To appear in special issue on molecular motors, Journal of Physics -
Condensed Matte
Optimal edge termination for high oxide reliability aiming 10kV SiC n-IGBTs
The edge termination design strongly affects the ability of a power device to support the desired voltage and its reliable operation. In this paper we present three appropriate termination designs for 10kV n-IGBTs which achieve the desired blocking requirement without the need for deep and expensive implantations. Thus, they improve the ability to fabricate, minimise the cost and reduce the lattice damage due to the high implantation energy. The edge terminations presented are optimised both for achieving the widest immunity to dopant activation and to minimise the electric field at the oxide. Thus, they ensure the long-term reliability of the device. This work has shown that the optimum design for blocking voltage and widest dose window does not necessarily give the best design for reliability. Further, it has been shown that Hybrid Junction Termination Extension structure with Space Modulated Floating Field Rings can give the best result of very high termination efficiency, as high as 99%, the widest doping variation immunity and the lowest electric field in the oxide
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Pyrolysis-GC×GC-TOFMS to characterize carbonaceous chondrites
Using pyrolysis-GCxGC-TOFMS to analyze organic carbon in carbonaceous chondrites gives a massive increase in both sensitivity and structural information from samples when compared to traditional Py-GC-MS
Nonperturbative approach to interfacial spin-orbit torques induced by Rashba effect
Current-induced spin-orbit torque (SOT) in normal metal/ferromagnet (NM/FM)
bilayers bears great promise for technological applications, but the
microscopic origin of purely interfacial SOTs in ultra-thin systems is not yet
fully understood. Here, we show that a linear response theory with a
nonperturbative treatment of spin-dependent interactions and impurity
scattering potential predicts damping-like SOTs that are strictly absent in
perturbative approaches. The technique is applied to a two-dimensional
Rashba-coupled ferromagnet (the paradigmatic model of a NM/FM interface), where
higher-order scattering processes encoding skew scattering from nonmagnetic
impurities allow for current-induced spin polarization with nonzero components
along all spatial directions. This is in stark contrast to previous results of
perturbative methods (neglecting skew scattering), which predict a coplanar
spin-polarization locked perpendicular to the charge current as a result of
conventional Rashba-Edelstein effect. Furthermore, the angular dependence of
ensuing SOTs and their dependence upon the scattering potential strength is
analysed numerically. Simple analytic expressions for the
spin-density--charge-current response function, and related SOT efficiencies,
are obtained in the weak scattering limit. We find that the extrinsic
damping-like torques driven by impurity scattering reaches efficiencies of up
to 7% of the field-like (Rashba-Edelstein) torque. Our microscopic theory shows
that bulk phenomena, such as the spin Hall effect, are not a necessity in the
generation of the damping-like SOTs of the type observed in experiments on
ultra-thin systems.Comment: 9 Pages, 4 figure
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