Charge-$2e$ Skyrmion condensate in a hidden order state

TL;DR

This paper explores a novel state where skyrmions in a mixed triplet and singlet $d$-density wave carry charge $2e$ and can condense into a non-BCS superconducting phase, revealing intertwined topological order and broken symmetry.

Contribution

It introduces a new theoretical framework for skyrmionic textures in a higher angular momentum density wave that can lead to unconventional superconductivity and quantized charge pumping.

Findings

Skyrmions carry charge 2e in the proposed state.

Condensation of skyrmions results in a non-BCS superconducting phase.

Quantum phase transition may involve deconfined quantum critical points.

Abstract

A higher angular momentum ($\ell =2$) $d$-density wave, a mixed triplet and a singlet, interestingly, admits skyrmionic textures. The Skyrmions carry charge $2e$ and can condense into a spin-singlet s-wave superconducting state. In addition, a charge current can be induced by a time-dependent inhomogeneous spin texture, leading to quantized charge pumping. The quantum phase transition between this mixed triplet $d$-density wave and skyrmionic superconducting condensate likely leads to deconfined quantum critical points. We suggest connections of this exotic state to electronic materials that are strongly correlated, such as the heavy fermion $\mathrm{URu_{2}Si_{2}}$. At the very least, we provide a concrete example in which topological order and broken symmetry are intertwined, which can give rise to non-BCS superconductivity.