Electronic structure and properties of superconducting materials with simple Fermi surfaces

TL;DR

This paper analyzes the electronic structures of various superconductors with simple Fermi surfaces to identify key features influencing superconductivity, challenging the emphasis on high density-of-states and highlighting the role of Fermi surface simplicity.

Contribution

It provides a comparative analysis of different superconducting materials focusing on Fermi surface topology and other electronic properties, proposing that simple Fermi surfaces can support superconductivity even with low density-of-states.

Findings

High density-of-states at the Fermi level is not essential for superconductivity.

Superconductivity can persist with simple Fermi surfaces despite low density-of-states.

Thermal disorder limits the maximum critical temperature independently of doping.

Abstract

The electronic structures of the ground state for several different superconducting materials, such as cuprates, conventional 3-dimensional superconductors, doped semiconductors and low-dimensional systems, are quite different and sometimes in contrast to what is supposed to make a superconductor. Properties like the Fermi-surface (FS) topology, density-of-states (DOS), stripes, electron-phonon coupling ($\lambda_{ep}$) and spin fluctuations ($\lambda_{sf}$) are analyzed in order to find clues to what might be important for the mechanism of superconductivity. A high DOS at $E_F$ is important for standard estimates of $\lambda's$, but it is suggested that superconductivity can survive a low DOS if the FS is simple enough. Superconducting fluctuations are plausible from coupling to long wave length modes in underdoped cuprates, where short coherence length is a probable obstacle for long-range superconductivity. Thermal disorder is recognized as a limiting factor for large $T_C$ independently of doping.