Mechanisms-collections of rigid elements coupled by perfect hinges which exhibit a zero-energy motion-motivate the design of a variety of mechanical metamaterials. We enlarge this design space by... Show moreMechanisms-collections of rigid elements coupled by perfect hinges which exhibit a zero-energy motion-motivate the design of a variety of mechanical metamaterials. We enlarge this design space by considering pseudo-mechanisms, collections of elastically coupled elements that exhibit motions with very low energy costs. We show that their geometric design generally is distinct from those of true mechanisms, thus opening up a large and virtually unexplored design space. We further extend this space by designing building blocks with bistable and tristable energy landscapes, realize these by 3D printing, and show how these form unit cells for multistable metamaterials. Show less
A spatially oscillating pair potential Delta(r) = Delta(0)e(2iK center dot r) with momentum K > Delta(0)/hv drives a deconfinement transition of the Majorana bound states in the vortex cores of... Show moreA spatially oscillating pair potential Delta(r) = Delta(0)e(2iK center dot r) with momentum K > Delta(0)/hv drives a deconfinement transition of the Majorana bound states in the vortex cores of a Fu-Kane heterostructure (a 3D topological insulator with Fermi velocity v, on a superconducting substrate with gap Delta(0), in a perpendicular magnetic field). In the deconfined phase at zero chemical potential the Majorana fermions form a dispersionless Landau level, protected by chiral symmetry against broadening due to vortex scattering. The coherent superposition of electrons and holes in the Majorana Landau level is detectable as a local density of states oscillation with wave vector root K-2 - (Delta(0)/hv)(2). The striped pattern also provides a means to measure the chirality of the Majorana fermions. Show less
