The effect of cracks on the superconducting transport current in thin films: The analogy with two-dimensional elasticity and plasticity

Simulations of arrays of resistively shunted Josephson junctions containing a crack of uncoupled junctions indicate that the crack can distort the supercurrent flow and provide a nucleation site at the crack tip for the formation of superconducting vortices at applied currents below the critical current of the homogeneous material. An analogy is established between the supercurrent distribution in two dimensions and the stress field distribution around the crack for antiplane mechanical loading. The analogy is used to show that the supercurrent distribution can be described analytically in terms of a Westergaard function used in elasticity theory. In addition, using a correspondence between the forces acting on a vortex and a crystal dislocation, models for screw dislocation emission from a crack tip are transposed to describe vortex emission from a crack tip. These lead to predictions for the pinning force required to prevent dissipation by vortex emission from the crack tip, as well as for the size of a vortex zone ahead of the crack for different values of the ratio of the applied current to the pinning force.

Download Full-text

Superfluid vortex-mediated mutual friction in non-homogeneous neutron star interiors

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3097 ◽

2020 ◽

Vol 499 (3) ◽

pp. 3690-3705

Author(s):

M Antonelli ◽

B Haskell

Keyword(s):

Neutron Star ◽

Normal Component ◽

Homogeneous Medium ◽

Outer Core ◽

Two Dimensions ◽

Pinning Force ◽

Mutual Friction ◽

Momentum Exchange ◽

Drag Forces ◽

Vortex Lines

ABSTRACT Understanding the average motion of a multitude of superfluid vortices in the interior of a neutron star is a key ingredient for most theories of pulsar glitches. In this paper, we propose a kinetic approach to compute the mutual friction force that is responsible for the momentum exchange between the normal and superfluid components in a neutron star, where the mutual friction is extracted from a suitable average over the motion of many vortex lines. As a first step towards a better modelling of the repinning and depinning processes of many vortex lines in a neutron star, we consider here only straight and non-interacting vortices: we adopt a minimal model for the dynamics of an ensemble of point vortices in two dimensions immersed in a non-homogeneous medium that acts as a pinning landscape. Since the degree of disorder in the inner crust or outer core of a neutron star is unknown, we compare the two possible scenarios of periodic and disordered pinscapes. This approach allows us to extract the mutual friction between the superfluid and the normal component in the star when, in addition to the usual Magnus and drag forces acting on vortex lines, also a pinning force is at work. The effect of disorder on the depinning transition is also discussed.

Download Full-text

Atomistic Study of Cleavage and Dislocation Emission in NiAl

MRS Proceedings ◽

10.1557/proc-364-389 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 4

Author(s):

M. Ludwig ◽

P. Gumbsch

Keyword(s):

Finite Element ◽

Mixed Mode ◽

Crack Tip ◽

Mode I ◽

Crack Plane ◽

Dislocation Emission ◽

Dislocation Generation ◽

Embedded Atom ◽

Atomistic Study ◽

Eam Potential

AbstractThe atomistic processes during fracture of NiAl are studied using a new embedded atom (EAM) potential to describe the region near the crack tip. To provide the atomistically modeled crack tip region with realistic boundary conditions, a coupled finite element - atomistic (FEAt) technique [1] is employed. In agreement with experimental observations, perfectly brittle cleavage is observed for the (110) crack plane. In contrast, cracks on the (100) plane either follow a zig-zag path on (110) planes, or emit dislocations. Dislocation generation is studied in more detail under mixed mode I/II loading conditions.

Download Full-text