Engineering topics
Crabtree, G. W.
Publications and source records attributed to Crabtree, G. W..
Large spin-orbit coupling and helical spin textures in 2D heterostructure [Pb 2 BiS 3 ][AuTe 2 ]
Two-dimensional heterostructures with strong spin-orbit coupling have direct relevance to topological quantum materials and potential applications in spin-orbitronics. In this work, we report on novel quantum phenomena in [Pb 2 BiS 3 ][AuTe 2 ], a new 2D strong spin-orbit coupling heterostructure system. Transport measurements reveal the spin-related carrier scattering is at odds with the Abrikosov-Gorkov model due to strong spin-orbit coupling. This is consistent with our band structure calculations which reveal a large spin-orbit coupling gap of ε so = 0.21 eV. Furthermore, the band structure is also characterized by helical-like spin textures which are mainly induced by strong spin-orbit coupling and the inversion symmetry breaking in the heterostructure system.
Vortex cutting in superconductors
Vortex cutting and reconnection is an intriguing and still-unsolved problem central to many areas of classical and quantum physics, including hydrodynamics, astrophysics, and superconductivity. Here, in this paper, we describe a comprehensive investigation of the crossing of magnetic vortices in superconductors using time dependent Ginsburg-Landau modeling. Within a macroscopic volume, we simulate initial magnetization of an anisotropic high temperature superconductor followed by subsequent remagnetization with perpendicular magnetic fields, creating the crossing of the initial and newly generated vortices. The time resolved evolution of vortex lines as they approach each other, contort, locally conjoin, and detach, elucidates the fine details of the vortex-crossing scenario under practical situations with many interacting vortices in the presence of weak pinning. Finally, our simulations also reveal left-handed helical vortex instabilities that accompany the remagnetization process and participate in the vortex crossing events.
Enhancing superconducting critical current by randomness
The key ingredient of high critical currents in a type-II superconductor is defect sites that pin vortices. Here, we demonstrate that a random pinscape, an overlooked pinning system in nanopatterned superconductors, can lead to a substantially larger critical current enhancement at high magnetic fields than an ordered array of vortex pin sites. We reveal that the better performance of a random pinscape is due to the variation of the local density of its pinning sites, which mitigates the motion of vortices. This is confirmed by achieving even higher enhancement of the critical current through a conformally mapped random pinscape, where the distribution of the local density of pinning sites is further enlarged. Our findings highlight the potential of random pinscapes in enhancing the superconducting critical currents of applied superconductors in which random pin sites of nanoscale defects emerging in the materials synthesis process or through ex-situ irradiation are the only practical choice for large-scale production. Our results may also stimulate research on effects of a random pinscape in other complementary systems such as colloidal crystals, Bose-Einstein condensates, and Luttinger liquids.
Temperature-Dependent Three-Dimensional Anisotropy of the Magnetoresistance in WTe 2
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The Social Science and Engineering of Research Practice.
The verdict is in: the methods of science can significantly enhance the effectiveness of creative teams. Just ask employers like Google and Facebook who are applying ideas from the social sciences to improve the performance of their organizations.1 Over the last few decades, social scientists, including psychologists, sociologists and anthropologists, have made important strides in developing a scientific understanding of how creative individuals and creative communities operate.
Rayleigh instability of confined vortex droplets in critical superconductors
Depending on the Ginzburg-Landau material parameter , superconductors can either be fully diamagnetic if k < 1√2 (type I superconductors) or accommodate magnetic field in the form of Abrikosov vortices if k > 1√2 (type II superconductors).1,2 At Bogomolny critical point, k = kc = 1 √2, a state, infinitely degenerated with respect to vortex spatial configurations, arises.3,4 While conventional type I and type II superconductors are investigated in depth, a thorough understanding of magnetic behaviour in the near-Bogomolny critical regime at k ~ kc is still lacking. Here we report that in restricted systems the critical regime expands over a finite interval of k forming critical superconducting state. We show that in this state, in a sample with dimensions comparable with the vortex core size, vortices merge into a multi-quanta droplet, which undergoes Rayleigh instability5 upon increasing k and decays by emitting single vortices. Superconducting vortices materialize Nielsen-Olesen singular solutions of the Abelian Higgs model pervasive in phenomena ranging from quantum electrodynamics to cosmology.6,7,8,9 Our work, revealing transient dynamics of Abrikosov-Nielsen-Olesen vortices in systems with boundaries, promises access to novel effects in quantum field theory via bench-top laboratory experiments.