Self-organised magnon condensation in quasi-1D edge-shared cuprates without external fields

TL;DR

This paper introduces a new mechanism for stabilizing multimagnon bound states in quasi-1D cuprates without external magnetic fields, supported by theory, simulations, and experimental data, with implications for quantum technologies.

Contribution

It proposes a novel intrinsic stabilization mechanism for multimagnon states in low-dimensional magnets, eliminating the need for external fields and broadening experimental and technological possibilities.

Findings

Small interchain couplings act as internal magnetic fields.

Magnon condensation occurs at zero external field.

Applicable to several representative materials.

Abstract

Multimagnon bound states were predicted nearly a century ago and have since been a key topic in condensed matter physics due to their intriguing quantum properties. However, their realization in natural materials remains elusive, especially in low-dimensional quantum magnets, where stabilizing them is particularly challenging due to the traditionally required extreme external magnetic fields. Therefore, we introduce a novel mechanism that enables the stabilization of multimagnon bound states in quasi-one-dimensional edge-shared cuprates. Our theoretical framework, supported by numerical simulations and experimental data, demonstrates that small antiferromagnetic interchain couplings act as effective internal magnetic fields, promoting a collinear antiferromagnetic order and enabling magnon condensation even at zero external field. This intrinsic stabilisation mechanism eliminates the need for high external fields, offering a platform that is more accessible for experimental realization. We validate this concept by applying it to representative materials such as Li$_2$CuO$_2$, Ca$_2$Y$_2$Cu$5$O$_{10}$, LiCuSbO$_4$, and PbCuSO$_4$(OH)$_2$. Beyond its experimental feasibility, this mechanism could drive advancements in magnon-based quantum computing, low-power spintronic devices, and high-speed magnonic circuits. Moreover, our findings reveal that small interchain and/or interlayer couplings can generally unlock previously overlooked magnetic phenomena, redefining the nature of magnetically ordered states and expanding the frontiers of quantum magnetism.