Electronic Structure Study Of Low Dimensional Systems With Angle Resolved Photoemission Spectroscopy

Author : Ji Dai
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (112 download)

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Download or read book Low-dimensional Electron Systems Studied by Angle- and Spin-resolved Photoemission Spectroscopy written by Ji Dai and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Materials in which many-body interactions, low-dimensional confinement, and/or strong spin-orbit coupling are present show a rich variety of phenomena, but are still poorly understood. Essential information about the origin of such phenomena can be obtained by measuring their electronic structure. This thesis presents an experimental study of the electronic structure of some low-dimensional and/or strongly correlated materials of current fundamental interest, using angle- and spin-resolved photoemission spectroscopy (ARPES and SARPES). In the introductory part, I present my work on two innovative textbook examples showing how interactions affect the band structure of a material: the coupling of electrons with phonons in a Debye distribution in a two-dimensional electron system (2DES) in ZnO, a wide-band-gap oxide semiconductor used in photovoltaic applications, and the splitting induced by strong spin-orbit coupling (SOC) in the bulk valence band of ZnTe, another important semiconductor used in optoelectronic devices. Then, in the rest of this thesis, I discuss my original results in three different low-dimensional systems of current interest: 1.The realisation of a 2DES at the (110) surface of SnO2, the first of its kind in a rutile structure. Tunability of its carrier density by means of temperature or Eu deposition and robustness against surface reconstructions and exposure to ambient conditions make this 2DES promising for applications. By means of a simple redox reaction on the surface, this work has proven that oxygen vacancies can dope the conduction band minimum at the surface of SnO2, solving a long-debated issue about their role in n-type doping in SnO2. 2.The study of topological surface states in M2Te2X (with M = Hf, Zr, or Ti; and X = P or As), a new family of three-dimensional topological metals, originating from SOC and being protected by time-reversal symmetry. Their electronic structure and spin texture, studied by ARPES and SARPES, reveal the presence of massless Dirac fermions giving rise to Dirac-node arcs. 3.The investigation of the quasi-one-dimensional heavy-fermion material YbNi4P2, which presents a second-order quantum phase transition from a ferromagnetic to a paramagnetic phase upon partial substitution of phosphorous by arsenide. Such a transition is expected to occur only in zero- or one-dimensional systems, but a direct measurement of the electronic structure of ferromagnetic quantum-critical materials was missing so far. By careful in-situ preparation and cleaning of the surface of YbNi4P2 single crystals, which are impossible to cleave, their electronic structure has been successfully measured by ARPES, thus effectively unveiling the quasi-one-dimensionality of YbNi4P2. Moreover, the protocol used to make this material accessible to ARPES can be readily generalised to other exotic materials lacking a cleavage plane.