# Dissertation/Thesis Abstract

Angle-Resolved Photoemission Spectroscopy Study of High Temperature Superconductor Cuprate, and Potential High Temperature Superconductors K-Doped p-Terphenyl and Trilayer Nickelate
by Li, Haoxiang, Ph.D., University of Colorado at Boulder, 2017, 114; 10642070
Abstract (Summary)

The macroscopic quantum phenomenology of superconductivity has attracted broad interest from both scientific research and applications. Many exotic physics found in the first high $T_C$ superconductor family cuprate remain unsolved even after 30 years of intense study. Angle-Resolved Photoemission Spectroscopy (ARPES) provides the direct probe to the major information of the electronic interactions, which plays the key role in these exotic physics including high $T_C$ superconductivity. ARPES is also the best tool to study the electronic structure in materials that potentially hold high $T_C$ superconductivity, providing insight for materials research and design. In this thesis, we present the ARPES study of the cuprate high $T_C$ superconductor Pb doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, and potential high $T_C$ superconductors K doped \textit{p}-terphenyl, and trilayer nickelate La$_4$Ni$_3$O$_{10}$. For Pb doped Bi2212, our study focuses on the key part of the electronic interactions---the self-energies. With the development of a novel 2-dimensional analysis technique, we present the first quantitative extraction of the fully causal complex self-energies. The extracted information reveals a conversion of the diffusive strange-metal correlations into a coherent highly renormalized state at low temperature followed by the enhancement of the number of states for pairing. We then further show how this can lead to a strong positive feedback effect that can stabilize and strengthen superconducting pairing. In K doped \textit{p}-terphenyl, we discover low energy spectral gaps that persist up to 120 K, consistent with potential Meissner effect signal from previous studies. Among a few potential origins for these gaps, we argue that the electron pairing scenario is most likely. For La$_4$Ni$_3$O$_{10}$, we present the Fermiology and electron dynamics of this material, and they show certain similarities to the cuprate electronic structure, as well as a few unique features.

Indexing (document details)
 Advisor: Dessau, Daniel S. Commitee: Cao, Gang, Michl, Josef, Nandkishore, Rahul, Reznik, Dmitry School: University of Colorado at Boulder Department: Physics School Location: United States -- Colorado Source: DAI-B 79/04(E), Dissertation Abstracts International Source Type: DISSERTATION Subjects: Condensed matter physics, Materials science Keywords: Angle-resolved, Cuprate, K-doped, Nickelate, P-terphenyl, Photoemission, Resolved, Superconductor, Superconductors, Temperature, Terphenyl, Trilayer Publication Number: 10642070 ISBN: 9780355543506