Chern-Simons superconductors and their instabilities

TL;DR

This paper develops a fermionic representation with Chern-Simons gauge fields to describe quantum antiferromagnets, revealing how instabilities in Chern-Simons superconductors signal transitions to quantum spin liquids and other exotic phases.

Contribution

It introduces a novel fermionic-Chern-Simons framework for quantum antiferromagnets, enabling analysis of ordered states, spin liquids, and phase transitions driven by frustration.

Findings

Chern-Simons superconductor states qualitatively match N{é}el order.

Instabilities in these states indicate confinement-deconfinement transitions.

Framework can describe both magnetic order and quantum spin liquids.

Abstract

Two-dimensional quantum antiferromagnets host rich physics, including long-range ordering, high-$T_c$ superconductivity, quantum spin liquid behavior, topological ordering, a variety of other exotic phases, and quantum criticalities. Frustrating perturbations in antiferromagnets may give rise to strong quantum fluctuations, challenging the theoretical understanding of the many-body ground state. Here we develop a method to describe the quantum antiferromagnets using fermionic degrees of freedom. The method is based on a formally exact mapping between spin exchange models and theories describing fermionic matter with the emergent $U(1)$ Chern-Simons gauge field. For the planar N\'{e}el state, this mapping self-consistently generates the Chern-Simons superconductor mean-field ground state of introduced spinless fermions. We systematically compare the Chern-Simons superconductor state with the planar N\'{e}el state at the level of collective modes as well as order parameters. We reveal qualitative and quantitative correspondences between these two states. We demonstrate that such a construction using the fractionalized excitations and Chern-Simons gauge field can not only describe the N\'{e}el order but can also be applied to study quantum spin liquids. Furthermore, we show that the confinement-deconfinement transitions from the N\'{e}el order to quantum spin liquids are signaled and characterized by the instabilities of Chern-Simons superconductors, driven by strong frustration. The results suggest observing and classifying the descendants of antiferromagnets, including other ordered states and unconventional superconductors, as well as emergent quantum spin liquids.