The chirality of edge states that form at the boundaries of a two-dimensional topological insulator imparts on them a fundamentally spin polarized character, with states of anti-parallel spins carrying electrons with opposite momenta. This project aims to take advantage of this spin-momentum locking to study various aspects of superconducting transport in these chiral edge states.
Our studies will begin with more basic aspects, such as observing robust superconductivity and seeing if a full Andreev bound state can be achieved. The nature of this transport will be investigated in detail with the idea of heading towards an unambiguous condensed matter based realization of the Majorana fermion, which is a particle that is its own antiparticle.
Such Majorana particles can take the form of a coherent superposition of zero-energy electron and hole excitations, which can be created for example in the induced superconducting gap in a topological insulator (TI). To explore for such states we will examine a variety of methods. These will include studying the current-phase relationship and the properties of the a.c. Josephson effect in superconductor/2D-TI/superconductor Josephson junctions, and exploring the affect of electrostatically tunable scattering in normal-TI-superconducting junctions that potentially host Majorana fermion bound states.
 S. Mi et al., Phys. Rev. B 87, 241405 (2013).