Riassunto analitico
Hole-doped copper oxide superconductors have been a subject of great interest in the field of condensed matter physics, primarily due to their extraordinary critical temperatures and the complex phase diagram. However, what truly distinguishes them and forms the core of this master’s thesis is their unconventional transport properties, which defy conventional expectations. In contrast to typical metals where the Fermi liquid theory characterizes electron behavior near the Fermi surface, cuprate superconductors exhibit properties that appear to violate Fermi-liquid theory. In particular, the failure of the Boltzmann transport equation, governing electron transport in conventional metals, emerges as a prominent aspect in the context of cuprates, and this breakdown will be the main focus of this thesis.
A comprehensive numerical investigation was conducted to analyze the transport properties (resistivity, Hall effect, high-field magnetoresistance) of cuprates. Specifically, two prominent cuprate metals, LSCO (La2-xSrxCuO4) and Bi2201 (Bi2Sr2CuO6+δ) were examined across a wide range of doping levels, spanning from the underdoped to the overdoped regime. Doping variation is a pivotal factor in the study of cuprates as it introduces non-trivial changes in the electronic ground state, and subsequently, in their transport properties. After defining the materials, transport properties are computed by numerically solving the Boltzmann transport equation within the relaxation time approximation. Special emphasis is placed on the so-called strange-metal phase, the normal state from which superconductivity emerges as temperature decreases, where the signatures of anomalous behaviour are most pronounced. The most significant outcome of our analysis is the persistent challenge in reconciling the observed transport properties within the framework of a conventional Boltzmann transport approach. Our findings indeed reinforce the conclusion that providing a comprehensive explanation for the transport properties of cuprates remains a formidable task, one that would appear to require a theoretical framework beyond the confines of conventional Boltzmann theory.
|