Interfaces and heterostructures with topological superconductors

Louisiana State University, Baton Rouge LA

Investigators

Abstract

TECHNICAL SUMMARY This award supports theoretical investigation of interfaces and heterostructures involving non-centrosymmetric superconductors. The PI will investigate the properties of the surface and edge states arising in such materials due to their topological properties and explore how these states are affected and can be controlled by creating structures that put them in contact with magnetic and other superconducting materials. The planned research is rooted in the PI's experience in collaborations with experimental groups, and in his involvement in the analysis of recently discovered unconventional superconductors without center of inversion. The PI will use an array of theoretical and computational methods to investigate the properties of such states. Previous work clearly showed that self-consistent treatment of the superconducting order is essential for the correct description of the bound states and will be implemented throughout the work. The PI will compute spectral features and magnetic properties of the bound states at the interfaces with normal metals, magnetic metals and insulators, and other superconductors, and will determine electrical and spin currents in biased junctions. The research will especially focus on the Josephson and proximity effects and on spin transport in such structures. These studies contribute to the knowledge base of topological materials enabling possible future technological applications. The research will provide a valuable learning environment for students who will develop analytical and computing skills that will prepare them for a variety of careers. NON-TECHNICAL SUMMARY This award supports theoretical investigation of robust states of matter that arise at interfaces and in artificially structured materials involving novel superconducting materials. Superconductivity, the ability to conduct current without heating, or dissipation, and magnetism, the property that allows the compass needle to point in the direction of magnetic field, are but two examples of features which enable functionality of our technology. Very recently, researchers started to focus on other ways electrons might organize themselves, so-called topological states of matter. These hold promise for potential technological applications beyond the capabilities of well-studied states, such as superconductivity and magnetism. In these new types of materials the enormously large collective of electrons is believed to support a new state of electronic matter that has properties that are robust to the normally deleterious effects of perturbations and defects. It is somewhat like a car tire: no matter how deformed it may be by pressing at the curb or a rock in the road, tracing around the outside of the tire one always encompasses the hole in the middle - an essential property of a tire. These topological quantum states appear most clearly when we look at the edges and boundaries of the sample. Technological applications of topological quantum states and the materials that exhibit them require understanding how to manipulate the signature states that live on surfaces and boundaries of the material. This project involves research and educational activities aimed to understand how to control the magnetic and electronic properties of the interfaces involving topological superconductors, materials which support both electrical current without dissipation throughout the bulk and the associated surface states that may be magnetized or carry magnetic currents. Topological superconductivity is believed to have been recently discovered in certain materials. Together with students, the PI will study how the useful features of topological states can be influenced and controlled by creating contacts between topological superconductors and other magnetic and superconducting materials. The PI will aslo study the effects of applied voltages and currents. This knowledge will provide advances in the fundamental understanding of how to manipulate topological quantum states near interfaces contributing to the intellectual foundations of new device technologies. The project includes international collaborations.