Chemistry and High Temperature Superconductivity

TL;DR

Over the past 25 years, multiple families of high-temperature superconductors with critical temperatures exceeding 23 K have been discovered, characterized by their chemical features and classified into two main types based on their nonmetallic content.

Contribution

The paper reviews seven families of high-temperature superconductors, discusses their chemical features, and analyzes the probability of discovering superconductors with Tc above 100 K or room temperature.

Findings

Seven families of high-Tc superconductors identified.

High nonmetallic content correlates with higher Tc.

Probability of room temperature superconductivity is very low.

Abstract

Seven distinct families of superconductors with critical temperatures at ambient pressure that equal or surpass the historic 23 K limit for Nb3Ge have been discovered in the last 25 years. Each family is reviewed briefly and their common chemical features are discussed. High temperature superconductors are distinguished by having a high (\geq 50%) content of nonmetallic elements and fall into two broad classes. 'Metal-nonmetal' superconductors require a specific combination of elements such as Cu-O and Fe-As which give rise to the highest known Tc's, probably through a magnetic pairing mechanism. 'Nonmetal-bonded' materials contain covalently-bonded nonmetal anion networks and are BCS-like superconductors. Fitting an extreme value function to the distribution of Tc values for the known high-Tc families suggests that the probability of a newly discovered superconductor family having maximum Tc > 100 K is ~0.1-1%, decreasing to ~0.02-0.2% for room temperature superconductivity.