Protection of Unconventional Superconductivity from Disorder

TL;DR

This paper investigates how certain electronic band structures can inherently protect unconventional superconductivity from disorder-induced suppression, highlighting specific lattice types where this robustness occurs.

Contribution

It identifies generic band structure properties that enable robust unconventional superconductivity despite disorder, supported by case studies on kagome and Lieb lattices.

Findings

Kagome and Lieb lattices support weak $T_c$ suppression by disorder.

Square and honeycomb lattices do not protect against disorder effects.

Potential material candidates for robust unconventional superconductivity are discussed.

Abstract

Unconventional superconductivity is a desirable state of matter due to its potential for high transition temperatures $T_{\mathrm{c}}$ and associated favorable superconducting properties. However, the sign-changing nature of the order parameter of unconventional superconductors renders their condensates fragile to disorder, an inevitability in real materials. We uncover the generic properties of electronic band structures and associated Bloch weights able to support robust unconventional superconductivity. We demonstrate this property in several case studies of the kagome and Lieb lattices, showing how unconventional superconductors exhibit unusually weak $T_{\mathrm{c}}$ suppression by disorder, despite featuring fully compensated sign-changing order parameters. We contrast these results with those for unconventional superconductivity on the square and honeycomb lattices, which are unable to protect the condensates from disorder. Finally, we discuss material candidates for which this effect may be realized.