Electronic Structure of Unconventional Spin-Orbit Materials

Princeton University, Princeton NJ

Investigators

Abstract

Nontechnical Abstract: In an ordinary insulator, such as diamond, the occupied electronic levels are separated from unoccupied levels by a large energy barrier known as an energy gap. The energy gap prevents current flow when an electric field is applied. Recent research has uncovered a new class of insulators, called topological insulators and related Dirac materials, in which electrons can bypass the energy gap by moving out to the surfaces of the insulator. The energy vs. velocity behavior of these unusual electrons moving on the surface is light-like and follows Dirac equation. They exhibit many unusual quantum properties which can be harnessed to improve spin-based electronics, novel forms of quantum computing and energy-efficient devices in the longer run. This project focuses on studying the details of the novel quantum behaviors of electrons moving on the surface which will in turn not only lead to better understanding of the mechanism for doing so but also likely discover new pathways to applications. Students working on this project develop expertise in vacuum and nano-technology, material characterization methodologies, and advanced x-ray optics and electronic spectroscopy techniques preparing them for scientific careers in industry, academia or government laboratories. Outreach programs "Quantum Materials" and their integration with Princeton's REU and others such as "The Leadership Alliance Program: dedicated to increase diversity in academia" involve many minority and young students and facilitate their entry into the exciting world of modern science. Technical Abstract: Discovering new phases of matter with useful electronic or magnetic properties is an important goal in modern physics. In the past few years, research has uncovered a new phase of Dirac material dubbed "Topological Insulators". They exhibit quantum Hall-like effects without magnetic field and can be operated at room temperatures. In a topological insulator, these effects lead to surface states that have unusual spin textures with a linear relationship between energy and momentum (Dirac dispersion). Such states have been predicted to give rise to dissipationless (energy saving) spin currents, quantum entanglements and novel macroscopic behavior that obeys axionic electrodynamics rather than Maxwell's equations and can potentially realize exotic particles that can be used for fault tolerant quantum computing. Angle-resolved photoemission spectroscopy is used to study the quantum properties of several Bi-based 2D and 3D Dirac materials and their magnetic and superconducting doping-induced interaction and correlation effects under this project. When new materials with similar properties are discovered they are also studied in concert and compared with previously known materials. Students working on this project develop expertise in vacuum and nano-technology, material characterization methodologies, and advanced x-ray optics and spin- and photon-polarization resolved electronic spectroscopy techniques preparing them for future scientific careers in industry, academia or government laboratories. Outreach programs "Quantum Materials" and their integration with Princeton's REU and others such as "The Leadership Alliance Program: dedicated to increase diversity in academia" involve many minority and young students and facilitate their entry into the exciting world of modern science.