Numerically anchored theory for quantum materials
- Quantum materials retain manifestly quantum behavior at macroscopic scales, where regular materials can be approximated classically. Developing theories that describe these macroscopic quantum states is challenging due to Avogardo's number of quantum particles involved, which often experience strong correlations and symmetry confinements. Such theories must be tested by quantitatively comparing their results to experiments to determine if they can capture the correct physics. Studying these theories is the cornerstone of this thesis. The first section presents an investigation of the role of the rare-earth element $R$ in the newly-discovered superconducting infinite-layer nickelates RSr_(d)Ni_(1-d)O2. The electronic structure calculations of the parent compound RNiO2 with lanthanide substitution show a strong interplay between bandwidth renormalization, charge transfer, compensation, number of electron pockets, and magnetic exchange when traversing from La to Lu. These calculations gave rise to a microscopic model Hamiltonian built from Wannier downfolding, which then in turn was used to directly calculate the doping dependence of the superconducting nickelates. The second section of this thesis explores the rich landscape of surprising transport signatures in the EuX2Y2 compounds, where $X$ is a transition metal, and $Y$ is a pnictide. There are unexpectedly large contributions of the europium orbitals near the Fermi level which seem to play a significant role in transport, even though nominally, they should be far away in energy. The third section of this thesis examines spectroscopic signatures in high-disorder environments. Simulating x-ray spectroscopy and using statistical methods, a coordination number mechanism was developed for superionic conductivity in solid-state electrolytes. The study of theories that are quantitatively tied to experiments elucidates the complex behavior in multiple classes of quantum materials, and paves a path for future many-body studies.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Been, Emily May
|Degree committee member
|Degree committee member
|Stanford University, School of Humanities and Sciences
|Stanford University, Department of Physics
|Statement of responsibility
|Emily May Been.
|Submitted to the Department of Physics.
|Thesis Ph.D. Stanford University 2023.
- © 2023 by Emily May Been
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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