Nanoscale Engineering of Superconducting Proximity Effect in Topological Insulator Thin Films
Abstract
One of the most exciting frontiers in materials physics today involves creating layered structures of dissimilar materials to induce novel properties not present otherwise. Inducing superconductivity in a topological insulator (TI) by proximity to an s-wave superconductor (SC) has been predicted to induce topological superconducting state at the surface of the TI hosting Majorana modes. In addition to fundamental scientific interest, realizing topological superconductivity in proximity-based interfaces provides a foundation for their subsequent use in secure encryption and communication between warfighters, novel electronics and topological quantum computing. To-date, low-Tc SCs with small superconducting gap have predominantly been used in this effort, which limits the characterization and application to extremely low temperatures. This proposal aims to use molecular beam epitaxy to create and optimize TI/SC interfaces based on high-Tc Fe (Se,Te) SCs and doped Tis, and explore the emergent phenomena using spectroscopic-imaging scanning tunneling microscopy. The proposed experiments can lead to the first observation of superconducting proximity effect in Tis via coupling to superconducting Fe (Se,Te), and unveil the nature of unconventional superconductivity reported to emerge in heterostructures of non-superconducting FeTe and Bi2Te3. By carefully tuning the chemical composition of individual components, this work will provide further insight into open questions in superconducting proximity effect, including: ( 1) roles of various intrinsic parameters, (2) theoretically predicted diverging behavior of the induced pairing correlations and the induced gap that could lead to "gapless superconductivity" , (3) first measurement of the superconducting pairing symmetry and phonon proximity, and ( 4) separation of a zero-energy Majorana mode from conventional non-zero-energy modes inevitably present inside the magnetic vortex cores. The proposed experiments could enable creating heterostructures hosting topological superconductivity with larger gap and higher Tc, possibly above liquid nitrogen temperature by using a single layer of FeSe grown on SrTi03. Achieving these properties is a necessary step towards realizing more robust Majorana modes immune to decoherence.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 16, 2018
- Source ID
- W911NF1710399
Entities
People
- Ilija Zeljkovic
Organizations
- Army Contracting Command
- Boston College
- United States Army