Pseudo-spin-polarized topological superconductivity in kagome RbV$_3$Sb$_5$

TL;DR

This paper proposes that RbV$_3$Sb$_5$ is a nodal topological superconductor with pseudo-spin polarization, exhibiting Majorana flat bands and hysteresis, explaining recent experimental observations of magnetic hysteresis in this material.

Contribution

It introduces a novel topological superconducting state in RbV$_3$Sb$_5$, characterized by pseudo-spin polarization and Majorana modes, linking experimental hysteresis to topological properties.

Findings

RbV$_3$Sb$_5$ exhibits magnetic hysteresis in the superconducting state.

The superconducting state is proposed to be a nodal topological superconductor.

Majorana flat band modes are predicted at the boundary, detectable by tunneling.

Abstract

Kagome superconductors AV$_3$Sb$_5$ (A=K, Rb, Cs) have sparked considerable interest due to the presence of several intertwined symmetry-breaking phases within a single material. Interestingly, in a recent experiment, magnetic hysteresis was observed in the superconducting state through magnetoresistance measurements in RbV$_{3}$Sb$_{5}$ [Nature Comm \textbf{17}, 1310 (2026)], providing strong evidence of a spontaneous time-reversal symmetry breaking superconducting state. The magnetic hysteresis, combined with crystalline symmetry, imposes strong constraints on the possible pairing symmetries of the superconducting state. In this work, we propose that RbV$_3$Sb$_5$ is a nodal topological superconductor with pseudo-spin-polarized Cooper pairs. The pseudo-spin-polarized superconducting domains resemble the properties of ferromagnetic domains and induce hysteresis. Moreover, the nodal topological superconducting state possesses Majorana flat band modes at the sample boundary, which can be detected by tunneling experiments.