Upper critical fields in high-$T_{\mathrm{c}}$ superconductors

Abstract

Since the discovery of high-temperature superconductivity in cuprates, understanding the unconventional pairing mechanism has remained one of the most significant challenges. The upper critical field ($H_{c2}$) is an essential parameter for obtaining information on the pair-breaking mechanism, coherence length $\hat{I}¾$, and pairing symmetry, all of which are crucial for understanding unconventional superconducting mechanisms. Here, we provide a brief review of studies on $H_{c2}$ in several representative series of cuprate, iron-based, and nickelate superconductors. By comparing the behavior of $H_{c2}$ as a function of temperature, doping concentration, and anisotropy across these three major classes of superconductors, we hope to contribute to a better understanding of the complex pairing interactions in high-temperature superconductors.

invited review;18 pages, 14 figures