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Title: Discovery of Novel Dirac and Weyl Fermion Materials
Authors: Alidoust, Nasser
Advisors: Hasan, M. Zahid
Contributors: Physics Department
Keywords: Dirac Semimetals
Iridium Oxides
Strongly-Correlated Materials
Topological Insulators
Topological Kondo Insulators
Weyl Semimetals
Subjects: Physics
Condensed matter physics
Issue Date: 2017
Publisher: Princeton, NJ : Princeton University
Abstract: Discovering and investigating various fermionic quasiparticles with novel topological properties in solids has become an important front in condensed matter physics and materials science. Classical examples of such quasiparticles are the celebrated massless Dirac fermions discovered in topological insulators, which have challenged our fundamental understanding of quantum phases of matter by expanding them to the symmetry-protected topological phases. Following the discovery of topological insulators, the search for materials with Dirac fermions and novel functionalities has become a central theme in the studies of solid state systems. More variants of Dirac materials including topological crystalline insulators and three-dimensional Dirac semimetals have followed. These topological materials have not only introduced novel fundamental physical concepts and properties, but have also provided new routes to developing technological applications in nanoelectronics, spintronics, and topological quantum computing platforms. In this dissertation, we present the experimental discovery of a new topological phase of matter, the Weyl semimetal state, in the monoarsenides TaAs and NbAs. Furthermore, we study various material systems with strong electron interactions, and provide compelling evidence for the existence of robust surface states in samarium hexaboride SmB6, as well as identify a Z2 topological insulator state with intriguing Dirac fermions in the low-carrier strongly-correlated cerium monopnictides CeBi and CeSb. We also investigate the honeycomb iridate Na2IrO3 and uncover linearly dispersing metallic states on its surface. Finally, we image the spin-orbit split valence band and the deposited quantum well states of the monolayer and bulk transition metal dichalcogenides MoS2 and MoSe2. The measurements presented in this dissertation constitute the first realization of emergent Weyl fermions in nature, introduce various directions for future discoveries of topological phases in strongly-correlated materials, and shed light on the spin-orbit physics of two-dimensional atomic crystals. These findings expand the field of topological phases of matter to gapless semimetallic and strongly-correlated materials, and offer great promises for further technological applications of topological materials in diverse platforms such as fault-tolerant qubits and low-power electronic and spintronic devices.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog:
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Physics

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