The Search for Superconductors through Solid State Chemistry

Abstract

Despite intensive research in the field of superconductivity, there exists no "recipe" for finding new materials that superconduct. Although the most fundamental type of superconductivity is understood, we do not understand all the condition in which the phenomenon occurs. Therefore finding routes for discovering new superconductors is of high interest.

This thesis discusses a systematic search for new superconductors. This is done by comparing known superconductors and finding common similarities. Chapter 1 explains the most famous families of superconductors and explain common features appearing in most superconducting materials. Two different routes for searching for new superconductors are discussed. Chapter 2 focuses on crystal structure families that are commonly adopted by superconducting materials. In particular the <italic>XYZ</italic> family, a family of intermetallic phases with 1:1:1 stoichiometry will be investigated. Chapter 2 discusses the discovery of a new <italic>XYZ</italic> compound, HfCuGe2, the investigation of superconducting NaAlSi under pressure, and the discovery of a new high pressure phase of CaAuBi. The structural chemistry of <italic>XYZ</italic> phases is also discussed along with its relation to ionic and metallic radii.

Chapter 3 focuses on the idea that superconductivity often appears close to a structural, magnetic, or electronic instability. In this Chapter I predict superconductivity in Tl halide Perovskites, with the help of density functional theory. This is done by drawing an analogy to BaBiO3based superconductors. Furthermore the discovery of a new Hollandite phase, Rb0.17IrO2 is reported. Lastly, the magnetic instabilities and the newly discovered quantum phase transition in Fe doped Cr2B is presented.