Majorana zero modes and topologically nontrivial stripes induced by inhomogeneous superconductivity

What is it about?

In our study, we propose a novel platform where Majorana zero modes are localized at the ends of 1D “stripes” within a 2D topological insulator in proximity to a conventional superconductor. These stripes, which we call “topologically nontrivial stripes”, are induced by the inhomogeneous nature of the superconducting order parameter in the presence of a finite magnetic field parallel to the surface. The key idea is that the variation of the phase of the superconducting order parameter across the 2D platform creates regions where the system behaves effectively as a 1D system. In these regions, the topological invariant—which is a quantity that determines whether a system is in a topological phase—alternates between trivial and nontrivial values, depending on the phase of the order parameter. As a result, the Majorana zero modes localize at the ends of these quasi-1D regions, offering a new way to generate and manipulate them. This approach, which relies on the embedding of quasi-1D quantum states in a 2D platform, is conceptually different from the previously mentioned proposals based on 1D and 2D homogeneous superconductors.

Featured Image

Photo by Clark Van Der Beken on Unsplash

Photo by Clark Van Der Beken on Unsplash

Why is it important?

In condensed matter physics, Majorana zero modes are exotic quasiparticle excitations, named after the Italian physicist Ettore Majorana, which possess unique properties that make them potential building blocks for topological quantum computing. For instance, exchanging the position of Majorana zero modes is not commutative, in the sense that the final outcome depends on the order in which the exchanges are performed. Moreover, Majorana zero modes are “topologically protected”, that is, robust against disorder and other perturbations, due to their intrinsic topological nature. In other words, a Majorana mode cannot be destroyed by a local perturbation without changing the global topological makeup of the whole physical system. Intense research is devoted to exploiting these properties to build a topological quantum gate, which hopefully will become the fundamental building block of a so-called “topological” quantum computer.